ci: release version 0.2.0 [skip ci]

Reviewed-on: https://git.hiabuto.net/C3MA/CCMA/pulls/27

README.md

@@ -183,6 +183,80 @@ marker may share the last cell. CCMA removes both markers and clones the whole
 row, including its formatting, once per item. With no items, the template row
 is removed. A loop that is not closed in the same row is rejected.
 
+## Mail templates
+
+Every e-mail CCMA sends -- the welcome mail with its first invoice, dunning mails,
+SEPA pre-notifications and the data-review request -- is rendered from a plain text
+template. The shipped
+defaults are copied into the store's `templates/mail/` directory on first start
+and can be edited there or under Optionen -> E-Mail-Vorlagen. An existing file is
+never overwritten; a deleted one is restored from the shipped default.
+
+A template holds the subject in its first line and the message body after a blank
+line:
+
+```
+Betreff: {{reminder.name}} – {{claim.title}}
+
+Hallo {{member.first_name}},
+...
+```
+
+Placeholders use the same `{{ ... }}` syntax as the document templates. Which ones
+are available depends on the mail; the options dialog lists them per template and
+rejects unknown ones when saving. A line that contains nothing but placeholders
+which render empty (an optional hint, an empty list) is dropped, and
+`{{#claims}} ... {{/claims}}` repeats its content once per claim.
+
+## Data-review mailing
+
+"Datenüberprüfung anfragen" in the members tab asks members to check the data the
+club stores about them. Every member appears in the recipient list; preselected are
+the live memberships (accepted, active, suspended, resigned at year's end, honorary)
+that have an e-mail address. Members without one are skipped and reported.
+
+Each recipient gets one mail listing their own record -- number, name, nickname,
+birth date, contact data, address, status, member since, payment frequency, and the
+bank details only for members who have any. A field with no value is printed as
+`(nicht hinterlegt)` so the gap is visible, and the IBAN is masked down to its
+country code and last four digits, which is enough to recognise the account. The
+mail closes with the reference to put on a transfer -- member number and full name,
+either of which identifies the payment on its own.
+
+The text comes from the `Datenüberprüfung` template. Besides the usual member and
+organization placeholders it offers `{{data.sheet}}` (the whole record, one field per
+line), `{{data.count}}`, `{{member.iban_masked}}`, `{{payment.reference}}` (the
+suggested transfer reference), `{{data.iban_hint}}` (the note about the shortened
+IBAN, filled only for members whose bank details are listed) and the repeat block
+`{{#data}}{{field.label}}: {{field.value}}{{/data}}` for a custom layout.
+
+Delivery follows the configured e-mail mode (local `.eml` files, direct send, or
+IMAP drafts); the run is confirmed once more with the recipient count because it
+cannot be taken back. Every mail is archived below the member's
+`files/documents/Datenpruefung/` directory and logged as a `data_review_email_sent`
+event. A member whose mail fails is reported as a warning and the run continues with
+the rest.
+
+## Read-only stores
+
+The member store may be mounted read-only -- the encrypted volume holding the
+member data does not have to be writable to look something up. CCMA detects this
+at startup by probing the store with an actual write, skips the housekeeper (every
+one of its passes writes) and opens in a read-only session: a permanent warning
+banner above the tabs, a "NUR LESEN" marker in the window title and status bar,
+and every write refused with one clear message instead of an operating system
+error.
+
+Program settings still save normally -- they live in the user's config directory,
+not in the store. Settings that belong to the store (club data, member numbers,
+reminders, e-mail, mail templates) are skipped with a notice. When the volume is
+remounted with write access, "Erneut prüfen" in the banner picks that up without a
+restart: title, status bar and banner drop their markers, and the housekeeper pass
+that was skipped at startup is offered right away.
+
+A store that was never initialized cannot be opened read-only: creating it needs
+write access, and CCMA says so instead of failing obscurely.
+
 ## Housekeeper rules
 
 The housekeeper runs every rule for every member. Built-in Python rules live in
@@ -217,4 +291,13 @@ only confirming actual dispatch starts the new payment deadline and adds an
 optional fee line item. A claim-level dunning hold suppresses automatic and
 manual reminder preparation until it is removed or expires.
 
+An overdue claim of a member with an active mandate is not dunned but reported as
+a direct debit to look into -- until a reminder for it has actually been sent. A
+sent reminder (typically the "Rücklastschrift" preset for a bounced debit) takes
+that claim off the direct-debit track for good: it is expected as a transfer by
+the stated deadline, so the housekeeper continues it in the ordinary dunning
+sequence, the SEPA run leaves it out and says so, and its dunning mail asks for a
+transfer even though the mandate is still active. Reverting the sent reminder puts
+the claim back into the direct-debit run.
+
 Do not place a real member store inside the source repository.

VERSION

@@ -1 +1 @@
-0.1.0-dev15
+0.2.0

pyproject.toml

@@ -42,6 +42,7 @@ ccma = [
     "assets/CHANGELOG.json",
     "assets/splash.png",
     "assets/templates/*",
+    "assets/mail_templates/*",
     "assets/themes/forest/**/*",
     "assets/themes/forest/*",
 ]

src/ccma/assets/CHANGELOG.json

@@ -38,7 +38,12 @@
       "Eine überfällige Lastschrift, für die bereits eine Rücklastschrift-Mahnung versandt wurde und deren Zahlungsfrist noch läuft, wird vom Hausmeister nicht mehr weiterhin als überfällig gemeldet, sondern als niedrig priorisierter Hinweis, dass die Klärung noch läuft.",
       "Im SEPA-Export lassen sich einzelne Lastschriften per Mehrfachauswahl von der CSV-/XML-/Info-Mail-Erstellung ausschließen (z. B. während eine Rücklastschrift geklärt wird), statt immer alle offenen Lastschriften einziehen zu müssen; standardmäßig sind alle ausgewählt.",
       "Mahnungs- und SEPA-Info-Mails müssen nicht mehr zwingend als lokale Datei gespeichert und von Hand in Thunderbird importiert werden: unter Optionen → E-Mail-Versand kann ein Postfach mit SMTP- und IMAP-Zugangsdaten hinterlegt werden, wahlweise mit direktem Versand, Ablage als Entwurf im Postfach oder einer Rückfrage bei jeder Erzeugung; die bisherige lokale Ablage bleibt als Standard erhalten.",
-      "Direkt versandte Mahnungen und SEPA-Info-Mails können zusätzlich automatisch in einen Gesendet-Ordner des Postfachs abgelegt werden. Für den Entwürfe- und den Gesendet-Ordner lässt sich die tatsächliche Ordnerliste live vom Server abrufen und per Dropdown auswählen; ein noch nicht vorhandener, frei eingegebener Ordner wird bei Bedarf automatisch angelegt."
+      "Direkt versandte Mahnungen und SEPA-Info-Mails können zusätzlich automatisch in einen Gesendet-Ordner des Postfachs abgelegt werden. Für den Entwürfe- und den Gesendet-Ordner lässt sich die tatsächliche Ordnerliste live vom Server abrufen und per Dropdown auswählen; ein noch nicht vorhandener, frei eingegebener Ordner wird bei Bedarf automatisch angelegt.",
+      "Die Texte aller erzeugten E-Mails (Willkommen, Mahnung, SEPA-Vorabinformation) stecken jetzt in bearbeitbaren Vorlagen: Sie werden als Standard mitgeliefert, landen beim ersten Start im Mitglieder-Store unter templates/mail/ und können unter Optionen → E-Mail-Vorlagen mit Betreff, Text und Platzhaltern angepasst oder auf den Standardtext zurückgesetzt werden.",
+      "Für neue Mitglieder kann direkt aus der Mitgliederakte eine Willkommens- und Erstrechnungsmail erzeugt werden: Sie begrüßt das Mitglied, nennt Mitgliedsnummer und Beginn der Mitgliedschaft und stellt die noch offenen Forderungen (Aufnahmegebühr und erster Beitrag) mit Zahlungshinweis zusammen; einzelne Forderungen lassen sich abwählen und die fertige Mail vorab ansehen.",
+      "CCMA startet jetzt auch, wenn der Mitglieder-Store schreibgeschützt eingebunden ist (z. B. ein nur lesend gemountetes Crypt-Laufwerk): Die Daten lassen sich wie gewohnt ansehen, der Hausmeister wird übersprungen und alle schreibenden Aktionen werden mit einer verständlichen Meldung abgelehnt statt mit einem Systemfehler. Ein dauerhaft sichtbarer Warnhinweis über den Tabs sowie Markierungen in Fenstertitel und Statusleiste weisen auf den Nur-Lese-Betrieb hin; wird der Store wieder mit Schreibrechten eingebunden, genügt „Erneut prüfen“ ohne Neustart.",
+      "Über „Datenüberprüfung anfragen“ in der Mitgliederliste kann eine Bitte um Datenprüfung an beliebig viele Mitglieder auf einmal verschickt werden: Jede Mail listet den eigenen Datensatz des Empfängers auf (fehlende Angaben werden als solche ausgewiesen, die IBAN nur mit den letzten vier Stellen), vorausgewählt sind alle laufenden Mitgliedschaften mit E-Mail-Adresse. Text und Betreff stammen aus der neuen Vorlage „Datenüberprüfung“; jede Mail wird in der Mitgliederakte archiviert und in der Chronik vermerkt. Die Mail nennt außerdem die Zahlweise und den Verwendungszweck, den das Mitglied bei Überweisungen angeben soll (Mitgliedsnummer und voller Name).",
+      "Eine Forderung, für die bereits eine Mahnung bzw. Rücklastschrift-Zahlungserinnerung versandt wurde, wird nicht mehr als Lastschrift behandelt: Der Hausmeister meldet nach Ablauf der Zahlungsfrist die nächste Mahnstufe statt weiterhin „Einzug prüfen, eine Mahnung ist hier nicht vorgesehen“, der SEPA-Lauf zieht die Forderung nicht erneut ein (und weist die übersprungene Position aus) und die Mahnungsmail bittet um Überweisung, auch wenn das Lastschriftmandat weiterhin aktiv ist. Wird der Versand einer Mahnung zurückgenommen, steht die Forderung wieder für den Einzug bereit."
     ]
   },
   {

src/ccma/assets/mail_templates/datenpruefung.txt

@@ -0,0 +1,17 @@
+Betreff: Bitte prüfen: deine bei {{organization.name}} gespeicherten Daten
+
+Liebes Mitglied,
+
+folgende Daten haben wir über dich gespeichert. Wir bitten dich, diese einmal zu überprüfen und uns Änderungen ggf. mitzuteilen.
+
+{{data.sheet}}
+{{data.iban_hint}}
+
+Bitte gib bei Überweisungen an uns immer deine Mitgliedsnummer und/oder deinen vollen Namen (Vorname und Nachname) als Verwendungszweck an – dann können wir deine Zahlung sofort zuordnen:
+
+    {{payment.reference}}
+
+Stimmt etwas nicht oder fehlt eine Angabe? Dann antworte einfach auf diese Mail oder schreib uns an {{organization.email}}, dann pflegen wir die Änderung ein. Wenn alles passt, musst du nichts weiter tun.
+
+Viele Grüße
+{{signature}}

src/ccma/assets/mail_templates/mahnung.txt

@@ -0,0 +1,21 @@
+Betreff: {{reminder.name}} – {{claim.title}}
+
+Hallo {{member.first_name}},
+
+zu der Forderung „{{claim.title}}“ ist noch ein Betrag offen.
+
+Offener Betrag: {{claim.balance}} Euro
+Ursprünglich fällig: {{claim.due_date}}
+Neue Zahlungsfrist: {{reminder.payment_deadline}}
+{{reminder.items}}
+{{reminder.hint}}
+
+Bitte überweise den offenen Betrag unter Angabe deiner Mitgliedsnummer an:
+IBAN: {{organization.iban}}
+BIC: {{organization.bic}}
+Verwendungszweck: {{payment.reference}}
+
+Sollte sich deine Zahlung mit dieser Nachricht überschnitten haben, betrachte sie bitte als gegenstandslos.
+
+Viele Grüße
+{{signature}}

src/ccma/assets/mail_templates/sepa-info.txt

@@ -0,0 +1,16 @@
+Betreff: SEPA-Lastschrift {{organization.name}} – {{debit.collection_date}}
+
+Hallo {{member.first_name}},
+
+hiermit informieren wir dich, dass wir den folgenden Betrag per SEPA-Lastschrift einziehen werden:
+
+Betrag: {{debit.amount}} Euro
+Einzugsdatum: {{debit.collection_date}}
+Verwendungszweck: {{debit.purpose}}
+Mandatsreferenz: {{debit.mandate_reference}}
+Gläubiger-Identifikationsnummer: {{organization.creditor_id}}
+
+Sollten die Angaben nicht stimmen, melde dich bitte zeitnah bei uns.
+
+Viele Grüße
+{{signature}}

src/ccma/assets/mail_templates/willkommen.txt

@@ -0,0 +1,25 @@
+Betreff: Willkommen im Club, {{member.first_name}} – deine Mitgliedschaft und der erste Beitrag
+
+Hallo {{member.first_name}},
+
+herzlich willkommen bei {{organization.name}}! Der Vorstand hat deine Aufnahme beschlossen: Ab dem {{membership.start_date}} bist du offiziell Mitglied. Wir freuen uns sehr, dich an Bord zu haben.
+
+Deine Mitgliedsnummer lautet {{member.number}}. Damit ordnen wir Zahlungen und Rückfragen sofort zu – am besten schreibst du sie dir kurz auf.
+
+Damit auch die Buchhaltung glücklich ist, kommt hier deine erste Rechnung. Deine Zahlweise ist „{{member.payment_frequency}}“, offen sind aktuell:
+
+{{claims.list}}
+
+Gesamtbetrag: {{claims.total}} Euro
+Zahlbar bis: {{claims.first_due_date}}
+
+{{payment.instructions}}
+
+Und jetzt zum wichtigen Teil: Der Club lebt von den Leuten, die mitmachen. Komm zu den Clubabenden vorbei, bring deine Projekte mit, frag Löcher in Bäuche und teile, was du weißt. Es gibt keine dummen Fragen, nur ungelötete Ideen.
+
+Wenn etwas unklar ist, antworte einfach auf diese Mail oder schreib uns an {{organization.email}} – wir helfen gerne weiter.
+
+Viel Spaß, viel Neugier und happy hacking!
+
+Viele Grüße
+{{signature}}

src/ccma/domain/contributions.py

@@ -160,6 +160,22 @@ def reminder_items_total(reminder: dict[str, Any]) -> Decimal:
     )
 
 
+def claim_was_dunned(data: ContributionData, claim: dict[str, Any]) -> bool:
+    """True once a reminder for this claim has actually gone out. Such a claim has
+    left the direct-debit track: the collection failed (or never happened), the member
+    was asked in writing to pay it, and the money is expected as a transfer by the
+    stated deadline. Quietly collecting it a second time is exactly what the dunning
+    letter says will not happen, so both the SEPA run and the housekeeper ask this
+    before treating a claim as one the mandate still covers."""
+    claim_id = str(claim.get("claim_id", ""))
+    if not claim_id:
+        return False
+    return any(
+        str(reminder.get("claim_id", "")) == claim_id and str(reminder.get("status", "")) == "sent"
+        for reminder in data.reminders
+    )
+
+
 def contribution_override_covers_month(override: dict[str, Any], month: str) -> bool:
     valid_from = str(override.get("valid_from", ""))
     valid_until = str(override.get("valid_until", "") or "")

src/ccma/domain/mail_templates.py

@@ -0,0 +1,437 @@
+from __future__ import annotations
+
+import re
+from dataclasses import dataclass
+from pathlib import Path
+
+SUBJECT_HEADER = "Betreff:"
+BUILTIN_TEMPLATE_ROOT = Path(__file__).resolve().parent.parent / "assets" / "mail_templates"
+PLACEHOLDER_PATTERN = re.compile(r"\{\{\s*([a-z][a-z0-9_.]*)\s*\}\}", re.IGNORECASE)
+# A repeat block either wraps a single line ("{{#claims}}- {{claim.title}}{{/claims}}")
+# or spans several lines with the markers on their own lines; both render one copy of
+# the block per entry.
+# Matches a single repeat marker, opening or closing. The placeholder pattern
+# deliberately does not, so unbalanced markers need a check of their own -- they
+# would otherwise survive validation and end up verbatim in a sent mail.
+MARKER_PATTERN = re.compile(r"\{\{\s*([#/])\s*([a-z][a-z0-9_.]*)\s*\}\}", re.IGNORECASE)
+BLOCK_PATTERN = re.compile(
+    r"\{\{\s*#\s*([a-z][a-z0-9_.]*)\s*\}\}[ \t]*\n?(.*?)\{\{\s*/\s*\1\s*\}\}[ \t]*(\n?)",
+    re.IGNORECASE | re.DOTALL,
+)
+
+
+class MailTemplateError(RuntimeError):
+    pass
+
+
+@dataclass(frozen=True, slots=True)
+class MailTemplate:
+    subject: str
+    body: str
+
+
+@dataclass(frozen=True, slots=True)
+class MailTemplateBlock:
+    name: str
+    description: str
+    # Placeholder name -> short explanation, valid inside this block only.
+    placeholders: tuple[tuple[str, str], ...]
+    # The line the inserted block starts out with. It makes the inserted snippet a
+    # working block that renders real content -- the board edits this line rather
+    # than having to write the whole construct by hand.
+    sample: str
+
+    @property
+    def snippet(self) -> str:
+        return f"{{{{#{self.name}}}}}\n{self.sample}\n{{{{/{self.name}}}}}\n"
+
+
+@dataclass(frozen=True, slots=True)
+class PlaceholderEntry:
+    """One row of the options dialog's placeholder chooser: what it reads as, and
+    what double-clicking it puts into the template."""
+
+    label: str
+    snippet: str
+    description: str
+    indented: bool = False
+
+
+@dataclass(frozen=True, slots=True)
+class MailTemplateSpec:
+    key: str
+    label: str
+    filename: str
+    description: str
+    # Placeholder name -> short explanation, shown as editing help in the options
+    # dialog. The mail services must supply exactly these keys, so this doubles as
+    # the contract a stored template is validated against.
+    placeholders: tuple[tuple[str, str], ...]
+    blocks: tuple[MailTemplateBlock, ...] = ()
+
+
+BASE_PLACEHOLDERS: tuple[tuple[str, str], ...] = (
+    ("member.first_name", "Vorname"),
+    ("member.last_name", "Nachname"),
+    ("member.full_name", "Vor- und Nachname"),
+    ("member.nickname", "Nickname"),
+    ("member.number", "Mitgliedsnummer"),
+    ("member.email", "E-Mail-Adresse"),
+    ("member.status", "Mitgliedsstatus"),
+    ("member.accepted_at", "Datum des Aufnahmebeschlusses"),
+    ("member.started_at", "Mitglied seit"),
+    ("member.application_date", "Antragsdatum"),
+    ("member.payment_frequency", "Zahlweise"),
+    ("member.address_line", "Anschrift in einer Zeile"),
+    ("member.iban", "IBAN des Mitglieds"),
+    ("member.mandate_reference", "Mandatsreferenz"),
+    ("member.mandate_active", "Lastschriftmandat aktiv (Ja/Nein)"),
+    ("organization.name", "Vereinsname"),
+    ("organization.address_line", "Anschrift des Vereins"),
+    ("organization.email", "E-Mail-Adresse des Vereins"),
+    ("organization.website", "Website des Vereins"),
+    ("organization.iban", "IBAN des Vereins"),
+    ("organization.bic", "BIC des Vereins"),
+    ("organization.creditor_id", "Gläubiger-Identifikationsnummer"),
+    ("current_date", "Heutiges Datum"),
+    ("signature", "Signatur aus dem Versandfenster"),
+)
+
+# The fields a member can check but which no other mail needs, so they stay out of
+# BASE_PLACEHOLDERS: the data-review mail is the one that prints the whole record.
+MEMBER_RECORD_PLACEHOLDERS: tuple[tuple[str, str], ...] = (
+    ("member.birth_date", "Geburtsdatum"),
+    ("member.phone", "Telefonnummer"),
+    ("member.street", "Straße und Hausnummer"),
+    ("member.address_addition", "Adresszusatz"),
+    ("member.postal_code", "Postleitzahl"),
+    ("member.city", "Ort"),
+    ("member.country", "Land"),
+    ("member.account_holder", "Kontoinhaber"),
+    ("member.iban_masked", "IBAN, bis auf die letzten vier Stellen maskiert"),
+    ("member.mandate_signed_at", "Datum der Mandatserteilung"),
+)
+
+CLAIM_ITEM_PLACEHOLDERS: tuple[tuple[str, str], ...] = (
+    ("claim.title", "Bezeichnung der Forderung"),
+    ("claim.description", "Beschreibung inkl. abgerechnetem Zeitraum"),
+    ("claim.due_date", "Fälligkeitsdatum"),
+    ("claim.amount", "Gesamtbetrag der Forderung"),
+    ("claim.balance", "Noch offener Betrag"),
+)
+
+MAIL_TEMPLATES: tuple[MailTemplateSpec, ...] = (
+    MailTemplateSpec(
+        key="welcome",
+        label="Willkommen & Erstrechnung",
+        filename="willkommen.txt",
+        description=(
+            "Begrüßung neuer Mitglieder mit Mitgliedsnummer, Beginn der Mitgliedschaft "
+            "und den ersten offenen Forderungen (Aufnahmegebühr und erster Beitrag)."
+        ),
+        placeholders=BASE_PLACEHOLDERS
+        + (
+            (
+                "membership.start_date",
+                "Beginn der Mitgliedschaft; ist noch keiner erfasst, der 1. des auf den "
+                "Aufnahmebeschluss folgenden Monats",
+            ),
+            ("claims.list", "Alle ausgewählten Forderungen als Liste, eine je Zeile"),
+            ("claims.total", "Summe der ausgewählten Forderungen"),
+            ("claims.count", "Anzahl der ausgewählten Forderungen"),
+            ("claims.first_due_date", "Früheste Fälligkeit der ausgewählten Forderungen"),
+            ("payment.instructions", "Zahlungshinweis passend zum Lastschriftmandat"),
+            ("payment.reference", "Vorgeschlagener Verwendungszweck"),
+        ),
+        blocks=(
+            MailTemplateBlock(
+                name="claims",
+                description="Wiederholt sich je ausgewählter Forderung",
+                placeholders=CLAIM_ITEM_PLACEHOLDERS,
+                sample="{{claim.description}} (fällig {{claim.due_date}}): {{claim.balance}} Euro",
+            ),
+        ),
+    ),
+    MailTemplateSpec(
+        key="reminder",
+        label="Mahnung",
+        filename="mahnung.txt",
+        description=(
+            "Begleitmail zu einer Mahnung bzw. Zahlungserinnerung. Wird beim Versand "
+            "mit der jeweiligen Mahnstufe, Frist und den Mahnpositionen gefüllt."
+        ),
+        placeholders=BASE_PLACEHOLDERS
+        + CLAIM_ITEM_PLACEHOLDERS
+        + (
+            ("reminder.name", "Bezeichnung der Mahnstufe"),
+            ("reminder.level", "Nummer der Mahnstufe"),
+            ("reminder.payment_deadline", "Neue Zahlungsfrist"),
+            ("reminder.detail", "Freitext-Hinweis der Mahnung"),
+            ("reminder.hint", "Hinweiszeile, nur gefüllt wenn ein Freitext hinterlegt ist"),
+            ("reminder.items", "Mahnpositionen als Liste, eine je Zeile"),
+            ("reminder.fee_total", "Summe der Mahnpositionen"),
+            ("payment.instructions", "Zahlungshinweis passend zum Lastschriftmandat"),
+            ("payment.reference", "Vorgeschlagener Verwendungszweck"),
+        ),
+        blocks=(
+            MailTemplateBlock(
+                name="reminder.items",
+                description="Wiederholt sich je Mahnposition",
+                placeholders=(
+                    ("item.description", "Bezeichnung der Position"),
+                    ("item.amount", "Betrag der Position"),
+                ),
+                sample="{{item.description}}: {{item.amount}} Euro",
+            ),
+        ),
+    ),
+    MailTemplateSpec(
+        key="sepa",
+        label="SEPA-Vorabinformation",
+        filename="sepa-info.txt",
+        description=(
+            "Vorabinformation zu einem geplanten Lastschrifteinzug mit Betrag, "
+            "Einzugsdatum und Mandatsdaten."
+        ),
+        placeholders=BASE_PLACEHOLDERS
+        + (
+            ("debit.amount", "Einzuziehender Betrag"),
+            ("debit.collection_date", "Einzugsdatum"),
+            ("debit.purpose", "Verwendungszweck der Lastschrift"),
+            ("debit.mandate_reference", "Mandatsreferenz"),
+        ),
+    ),
+    MailTemplateSpec(
+        key="data_review",
+        label="Datenüberprüfung",
+        filename="datenpruefung.txt",
+        description=(
+            "Bitte an ein Mitglied, die über es gespeicherten Daten zu prüfen. Wird an "
+            "beliebig viele Mitglieder auf einmal verschickt und listet je Empfänger "
+            "dessen eigenen Datensatz auf."
+        ),
+        placeholders=BASE_PLACEHOLDERS
+        + MEMBER_RECORD_PLACEHOLDERS
+        + (
+            ("data.sheet", "Alle gespeicherten Daten als Liste, eine Zeile je Feld"),
+            ("data.count", "Anzahl der aufgeführten Felder"),
+            (
+                "data.iban_hint",
+                "Hinweis zur verkürzten IBAN, nur gefüllt wenn Bankdaten aufgeführt werden",
+            ),
+            (
+                "payment.reference",
+                "Vorgeschlagener Verwendungszweck aus Mitgliedsnummer und vollem Namen",
+            ),
+        ),
+        blocks=(
+            MailTemplateBlock(
+                name="data",
+                description="Wiederholt sich je gespeichertem Datenfeld",
+                placeholders=(
+                    ("field.label", "Bezeichnung des Feldes"),
+                    ("field.value", "Gespeicherter Wert"),
+                ),
+                sample="{{field.label}}: {{field.value}}",
+            ),
+        ),
+    ),
+)
+
+
+def placeholder_entries(key: str) -> list[PlaceholderEntry]:
+    """Rows for the placeholder chooser. Repeat blocks contribute a complete,
+    ready-to-edit block -- inserting one has to leave a working template behind,
+    not a description of one."""
+    spec = template_spec(key)
+    entries = [
+        PlaceholderEntry(f"{{{{{name}}}}}", f"{{{{{name}}}}}", description)
+        for name, description in spec.placeholders
+    ]
+    for block in spec.blocks:
+        entries.append(
+            PlaceholderEntry(
+                f"{{{{#{block.name}}}}} … {{{{/{block.name}}}}}", block.snippet, block.description
+            )
+        )
+        entries.extend(
+            PlaceholderEntry(f"{{{{{name}}}}}", f"{{{{{name}}}}}", description, indented=True)
+            for name, description in block.placeholders
+        )
+    return entries
+
+
+def template_spec(key: str) -> MailTemplateSpec:
+    for spec in MAIL_TEMPLATES:
+        if spec.key == key:
+            return spec
+    raise MailTemplateError(f"Unbekannte E-Mail-Vorlage: {key}")
+
+
+def default_mail_template(key: str) -> MailTemplate:
+    spec = template_spec(key)
+    path = BUILTIN_TEMPLATE_ROOT / spec.filename
+    try:
+        return parse_mail_template(path.read_text(encoding="utf-8"))
+    except OSError as exc:
+        raise MailTemplateError(
+            f"Die mitgelieferte Vorlage „{spec.label}“ konnte nicht gelesen werden: {exc}"
+        ) from exc
+
+
+def parse_mail_template(text: str) -> MailTemplate:
+    """Templates are plain text files whose first line carries the subject
+    ("Betreff: ..."), followed by a blank line and the message body -- readable and
+    editable with any text editor, just like the rest of the store."""
+    lines = text.replace("\r\n", "\n").replace("\r", "\n").split("\n")
+    subject = ""
+    if lines and lines[0].strip().casefold().startswith(SUBJECT_HEADER.casefold()):
+        subject = lines[0].split(":", 1)[1].strip()
+        lines = lines[1:]
+        if lines and not lines[0].strip():
+            lines = lines[1:]
+    return MailTemplate(subject, "\n".join(lines).strip("\n"))
+
+
+def serialize_mail_template(subject: str, body: str) -> str:
+    normalized = body.replace("\r\n", "\n").replace("\r", "\n").strip("\n")
+    return f"{SUBJECT_HEADER} {subject.strip()}\n\n{normalized}\n"
+
+
+def render_mail_template(
+    template: MailTemplate,
+    values: dict[str, str],
+    repeats: dict[str, list[dict[str, str]]] | None = None,
+) -> MailTemplate:
+    subject = _render_line(template.subject, values)
+    body = _render_blocks(template.body, values, repeats or {})
+    return MailTemplate(subject.strip(), _render_text(body, values))
+
+
+def validate_block_markers(key: str, subject: str, body: str) -> None:
+    """Checks that every {{#block}} is closed by its own {{/block}} and that no
+    stray marker is left over. An unbalanced marker is not a placeholder, so it
+    renders as itself -- the recipient would read "{{#claims}}" in their mail."""
+    spec = template_spec(key)
+    known = {block.name.casefold(): block.name for block in spec.blocks}
+    for match in MARKER_PATTERN.finditer(subject):
+        raise MailTemplateError(
+            f"Wiederholungsblöcke sind im Betreff nicht möglich: {match.group(0)}"
+        )
+    open_marker: tuple[str, str] | None = None
+    for match in MARKER_PATTERN.finditer(body):
+        kind, name = match.group(1), match.group(2)
+        if name.casefold() not in known:
+            raise MailTemplateError(
+                f"Unbekannter Wiederholungsblock: {match.group(0)}. Verfügbar: "
+                + (", ".join(f"{{{{#{value}}}}}" for value in known.values()) or "keine")
+            )
+        if kind == "#":
+            if open_marker is not None:
+                raise MailTemplateError(
+                    f"Wiederholungsblöcke können nicht ineinander verschachtelt werden: "
+                    f"{{{{#{open_marker[1]}}}}} ist noch offen, als {match.group(0)} beginnt."
+                )
+            open_marker = (kind, name)
+            continue
+        if open_marker is None:
+            raise MailTemplateError(
+                f"{match.group(0)} steht ohne zugehöriges {{{{#{name}}}}} in der Vorlage."
+            )
+        if open_marker[1].casefold() != name.casefold():
+            raise MailTemplateError(
+                f"{{{{#{open_marker[1]}}}}} wird durch {match.group(0)} geschlossen. "
+                f"Erwartet wird {{{{/{open_marker[1]}}}}}."
+            )
+        open_marker = None
+    if open_marker is not None:
+        raise MailTemplateError(
+            f"{{{{#{open_marker[1]}}}}} wird nicht geschlossen. Es fehlt "
+            f"{{{{/{open_marker[1]}}}}}."
+        )
+
+
+def validate_mail_template(key: str, subject: str, body: str) -> None:
+    """Rejects placeholders the mail service will never supply, so a typo surfaces
+    while editing the template instead of during a send run."""
+    spec = template_spec(key)
+    validate_block_markers(key, subject, body)
+    known = {name for name, _help in spec.placeholders}
+    block_names = {block.name for block in spec.blocks}
+    unknown: set[str] = set()
+    for block in spec.blocks:
+        block_known = known | {name for name, _help in block.placeholders}
+        for match in _blocks_of(body, block.name):
+            unknown.update(name for name in _placeholder_names(match) if name not in block_known)
+    remaining = body
+    for block_name in block_names:
+        remaining = _strip_blocks(remaining, block_name)
+    unknown.update(name for name in _placeholder_names(remaining) if name not in known)
+    unknown.update(name for name in _placeholder_names(subject) if name not in known)
+    if unknown:
+        raise MailTemplateError(
+            "Unbekannte Platzhalter in der Vorlage: " + ", ".join(sorted(unknown))
+        )
+    if not subject.strip():
+        raise MailTemplateError("Die Vorlage benötigt einen Betreff.")
+    if not body.strip():
+        raise MailTemplateError("Die Vorlage benötigt einen Text.")
+
+
+def _placeholder_names(text: str) -> set[str]:
+    return {match.group(1) for match in PLACEHOLDER_PATTERN.finditer(text)}
+
+
+def _blocks_of(text: str, name: str) -> list[str]:
+    return [
+        match.group(2)
+        for match in BLOCK_PATTERN.finditer(text)
+        if match.group(1).casefold() == name.casefold()
+    ]
+
+
+def _strip_blocks(text: str, name: str) -> str:
+    return BLOCK_PATTERN.sub(
+        lambda match: "" if match.group(1).casefold() == name.casefold() else match.group(0), text
+    )
+
+
+def _render_blocks(
+    body: str, values: dict[str, str], repeats: dict[str, list[dict[str, str]]]
+) -> str:
+    def expand(match: re.Match[str]) -> str:
+        name = match.group(1)
+        entries = next(
+            (rows for key, rows in repeats.items() if key.casefold() == name.casefold()), None
+        )
+        if entries is None:
+            return match.group(0)
+        block = match.group(2)
+        if block.endswith("\n"):
+            block = block[:-1]
+        rendered = [_render_text(block, {**values, **entry}) for entry in entries]
+        if not rendered:
+            return ""
+        return "\n".join(rendered) + match.group(3)
+
+    return BLOCK_PATTERN.sub(expand, body)
+
+
+def _render_text(text: str, values: dict[str, str]) -> str:
+    # A line that holds nothing but placeholders which all render empty (an optional
+    # hint, an empty list) is dropped instead of leaving a stray blank line behind.
+    rendered = []
+    for line in text.split("\n"):
+        replaced = _render_line(line, values)
+        if replaced.strip() or not line.strip() or not _placeholder_names(line):
+            rendered.append(replaced)
+            continue
+        if PLACEHOLDER_PATTERN.sub("", line).strip():
+            rendered.append(replaced)
+    return "\n".join(rendered)
+
+
+def _render_line(line: str, values: dict[str, str]) -> str:
+    return PLACEHOLDER_PATTERN.sub(
+        lambda match: values.get(match.group(1), match.group(0)), line
+    )

src/ccma/domain/placeholders.py

@@ -0,0 +1,80 @@
+from __future__ import annotations
+
+from datetime import datetime
+
+from ccma.domain.dates import format_date_for_display
+from ccma.domain.models import (
+    MEMBERSHIP_STATUS_LABELS,
+    PAYMENT_FREQUENCY_LABELS,
+    Member,
+)
+
+
+def base_placeholder_values(
+    member: Member,
+    organization: dict | None = None,
+    *,
+    created_at: datetime | None = None,
+) -> dict[str, str]:
+    """Member and organization placeholders shared by document templates and mail
+    templates, so the same `{{member.*}}`/`{{organization.*}}` names mean the same
+    thing in a dunning letter and in the e-mail that carries it."""
+    organization = organization if isinstance(organization, dict) else {}
+    timestamp = created_at or datetime.now().astimezone()
+    organization_address = " ".join(
+        part
+        for part in (
+            str(organization.get("street", "")),
+            str(organization.get("postal_code", "")),
+            str(organization.get("city", "")),
+        )
+        if part
+    )
+    return {
+        "current_date": format_date_for_display(timestamp.date().isoformat()),
+        "current_datetime": timestamp.strftime("%d.%m.%Y %H:%M"),
+        "member.id": member.member_id,
+        "member.number": member.member_number,
+        "member.first_name": member.first_name,
+        "member.last_name": member.last_name,
+        "member.nickname": member.nickname,
+        "member.full_name": member.display_name,
+        "member.email": member.email,
+        "member.phone": member.phone,
+        "member.birth_date": format_date_for_display(member.birth_date),
+        "member.status": MEMBERSHIP_STATUS_LABELS.get(member.status, member.status),
+        "member.accepted_at": format_date_for_display(member.accepted_at),
+        "member.started_at": format_date_for_display(member.membership_started_at),
+        "member.ended_at": format_date_for_display(member.membership_ended_at),
+        "member.application_date": format_date_for_display(member.application_date),
+        "member.payment_frequency": PAYMENT_FREQUENCY_LABELS.get(
+            member.payment_frequency, member.payment_frequency
+        ).capitalize(),
+        "member.street": member.street,
+        "member.address_addition": member.address_addition,
+        "member.postal_code": member.postal_code,
+        "member.city": member.city,
+        "member.country": member.country,
+        "member.address_line": " ".join(
+            part for part in (member.street, member.postal_code, member.city) if part
+        ),
+        "member.account_holder": member.account_holder,
+        "member.iban": member.iban,
+        "member.bic": member.bic,
+        "member.mandate_reference": member.mandate_reference,
+        "member.mandate_signed_at": format_date_for_display(member.mandate_signed_at),
+        "member.mandate_revoked_at": format_date_for_display(member.mandate_revoked_at),
+        "member.mandate_active": "Ja" if member.mandate_active else "Nein",
+        "organization.name": str(organization.get("name", "")),
+        "organization.street": str(organization.get("street", "")),
+        "organization.postal_code": str(organization.get("postal_code", "")),
+        "organization.city": str(organization.get("city", "")),
+        "organization.country": str(organization.get("country", "")),
+        "organization.address_line": organization_address,
+        "organization.email": str(organization.get("email", "")),
+        "organization.phone": str(organization.get("phone", "")),
+        "organization.website": str(organization.get("website", "")),
+        "organization.iban": str(organization.get("iban", "")),
+        "organization.bic": str(organization.get("bic", "")),
+        "organization.creditor_id": str(organization.get("creditor_id", "")),
+    }

src/ccma/rules/scripts/reminder_due.py

@@ -1,6 +1,6 @@
 from datetime import date, timedelta
 
-from ccma.domain.contributions import claim_balance, claim_status, money_text
+from ccma.domain.contributions import claim_balance, claim_status, claim_was_dunned, money_text
 from ccma.rules.api import RuleAction, RuleContext, task
 
 RULE_ID = "reminder-due"
@@ -18,12 +18,12 @@ DEFAULT_POLICY = {
 
 def evaluate(context: RuleContext) -> list[RuleAction]:
     """Owns the whole lifecycle of an overdue claim: a plain overdue notice during the
-    grace period, then either the postal dunning escalation or -- for members paying by
+    grace period, then either the postal dunning escalation or -- for a claim the
-    SEPA direct debit, where sending a dunning letter makes no sense -- a distinct
+    member's mandate still covers, where sending a dunning letter makes no sense -- a
-    "check the direct debit" notice. Falls back to the plain overdue notice whenever no
+    distinct "check the direct debit" notice. Falls back to the plain overdue notice
-    escalation applies (dunning hold active, or between reminder levels), so there is
+    whenever no escalation applies (dunning hold active, or between reminder levels),
-    always exactly one finding for an overdue claim, never both an overdue notice and a
+    so there is always exactly one finding for an overdue claim, never both an overdue
-    reminder notice at once."""
+    notice and a reminder notice at once."""
     policy = context.repository_config.get("reminder_policy") or DEFAULT_POLICY
     levels = sorted(policy.get("levels") or [], key=lambda value: int(value.get("level", 0)))
     grace_days = int(policy.get("grace_days_after_due", 7))
@@ -48,8 +48,11 @@ def evaluate(context: RuleContext) -> list[RuleAction]:
 
         escalation = None
         if days_overdue >= grace_days and not _hold_is_active(claim, context.today):
-            if context.member.mandate_active:
+            # A claim that was already dunned is no longer collected by direct debit --
-                escalation = _sepa_escalation(context, claim, claim_id, days_overdue)
+            # the member was asked to transfer it, so it continues in the ordinary
+            # dunning sequence even though the mandate itself is still active.
+            if context.member.mandate_active and not claim_was_dunned(context.contributions, claim):
+                escalation = _sepa_action(context, claim, claim_id, days_overdue)
             else:
                 escalation = _reminder_action(context, claim, claim_id, levels, policy)
         actions.append(escalation or _overdue_action(context, claim, claim_id, due, days_overdue))
@@ -72,13 +75,6 @@ def _overdue_action(context: RuleContext, claim, claim_id: str, due: date, days_
     )
 
 
-def _sepa_escalation(context: RuleContext, claim, claim_id: str, days_overdue: int) -> RuleAction:
-    pending = _latest_pending_reminder(context.contributions.reminders, claim_id, context.today)
-    if pending:
-        return _sepa_awaiting_action(context, claim, claim_id, *pending)
-    return _sepa_action(context, claim, claim_id, days_overdue)
-
-
 def _sepa_action(context: RuleContext, claim, claim_id: str, days_overdue: int) -> RuleAction:
     balance = money_text(claim_balance(context.contributions, claim))
     return task(
@@ -97,47 +93,6 @@ def _sepa_action(context: RuleContext, claim, claim_id: str, days_overdue: int)
     )
 
 
-def _sepa_awaiting_action(
-    context: RuleContext, claim, claim_id: str, reminder: dict, trigger_date: date
-) -> RuleAction:
-    """A Rücklastschrift-Mahnung (or any reminder) was already sent for this SEPA
-    claim and its own deadline hasn't expired yet -- staff already engaged, so this
-    must not keep nagging "check the direct debit" as if nothing had happened."""
-    name = str(reminder.get("name") or "Rücklastschrift")
-    balance = money_text(claim_balance(context.contributions, claim))
-    return task(
-        rule_id=RULE_ID,
-        member=context.member,
-        key_suffix=f"{claim_id}:sepa-awaiting",
-        severity="info",
-        code="sepa_debit_awaiting_deadline",
-        title=f"{context.member.display_name}: {name} versandt, Rücklastschriftklärung läuft",
-        detail=(
-            f"Forderung: {claim.get('title', claim_id)}. Offener Betrag: {balance} EUR. "
-            f"Zahlungsfrist bis {trigger_date.isoformat()} noch nicht abgelaufen."
-        ),
-        due_date=trigger_date,
-    )
-
-
-def _latest_pending_reminder(
-    reminders: list[dict], claim_id: str, today: date
-) -> tuple[dict, date] | None:
-    best: tuple[dict, date] | None = None
-    for item in reminders:
-        if str(item.get("claim_id", "")) != claim_id or str(item.get("status", "")) != "sent":
-            continue
-        try:
-            deadline = date.fromisoformat(str(item.get("payment_deadline", "")))
-        except ValueError:
-            continue
-        if today > deadline:
-            continue
-        if best is None or deadline > best[1]:
-            best = (item, deadline)
-    return best
-
-
 def _reminder_action(context: RuleContext, claim, claim_id: str, levels, policy) -> RuleAction | None:
     reminders = [
         item for item in context.contributions.reminders if str(item.get("claim_id", "")) == claim_id

src/ccma/services/documents.py

@@ -24,7 +24,8 @@ from ccma.domain.contributions import (
     reminder_items_total,
 )
 from ccma.domain.dates import format_date_for_display
-from ccma.domain.models import MEMBERSHIP_STATUS_LABELS, Member
+from ccma.domain.models import Member
+from ccma.domain.placeholders import base_placeholder_values
 from ccma.storage.repository import MemberRepository
 
 SUPPORTED_TEMPLATE_SUFFIXES = {".fodt", ".odt", ".ott"}
@@ -98,6 +99,7 @@ class DocumentService:
         if not template_path.is_file() or template_path.suffix.casefold() not in SUPPORTED_TEMPLATE_SUFFIXES:
             raise DocumentError("Das ausgewählte OpenDocument-Template ist nicht verfügbar.")
 
+        self.repository.assert_writable()
         member = self.repository.get_member(member_id)
         data = None
         claim = None
@@ -182,65 +184,14 @@ def _template_values(
     reminder: dict | None = None,
     organization: dict | None = None,
 ) -> tuple[dict[str, str], dict[str, list[dict[str, str]]]]:
-    organization = organization or {}
     created_at = datetime.now().astimezone()
-    created_date = format_date_for_display(created_at.date().isoformat())
+    values = base_placeholder_values(member, organization, created_at=created_at)
-    created_timestamp = created_at.strftime("%d.%m.%Y %H:%M")
+    values.update(
-    organization_address = " ".join(
+        {
-        part
+            "document.created_date": values["current_date"],
-        for part in (
+            "document.created_at": values["current_datetime"],
-            str(organization.get("street", "")),
-            str(organization.get("postal_code", "")),
-            str(organization.get("city", "")),
-        )
-        if part
-    )
-    values = {
-        "document.created_date": created_date,
-        "document.created_at": created_timestamp,
-        "current_date": created_date,
-        "current_datetime": created_timestamp,
-        "member.id": member.member_id,
-        "member.number": member.member_number,
-        "member.first_name": member.first_name,
-        "member.last_name": member.last_name,
-        "member.nickname": member.nickname,
-        "member.full_name": member.display_name,
-        "member.email": member.email,
-        "member.phone": member.phone,
-        "member.birth_date": format_date_for_display(member.birth_date),
-        "member.status": MEMBERSHIP_STATUS_LABELS.get(member.status, member.status),
-        "member.accepted_at": format_date_for_display(member.accepted_at),
-        "member.started_at": format_date_for_display(member.membership_started_at),
-        "member.ended_at": format_date_for_display(member.membership_ended_at),
-        "member.street": member.street,
-        "member.address_addition": member.address_addition,
-        "member.postal_code": member.postal_code,
-        "member.city": member.city,
-        "member.country": member.country,
-        "member.address_line": " ".join(
-            part for part in (member.street, member.postal_code, member.city) if part
-        ),
-        "member.account_holder": member.account_holder,
-        "member.iban": member.iban,
-        "member.bic": member.bic,
-        "member.mandate_reference": member.mandate_reference,
-        "member.mandate_signed_at": format_date_for_display(member.mandate_signed_at),
-        "member.mandate_revoked_at": format_date_for_display(member.mandate_revoked_at),
-        "member.mandate_active": "Ja" if member.mandate_active else "Nein",
-        "organization.name": str(organization.get("name", "")),
-        "organization.street": str(organization.get("street", "")),
-        "organization.postal_code": str(organization.get("postal_code", "")),
-        "organization.city": str(organization.get("city", "")),
-        "organization.country": str(organization.get("country", "")),
-        "organization.address_line": organization_address,
-        "organization.email": str(organization.get("email", "")),
-        "organization.phone": str(organization.get("phone", "")),
-        "organization.website": str(organization.get("website", "")),
-        "organization.iban": str(organization.get("iban", "")),
-        "organization.bic": str(organization.get("bic", "")),
-        "organization.creditor_id": str(organization.get("creditor_id", "")),
         }
+    )
     repeats: dict[str, list[dict[str, str]]] = {}
     if claim is not None and data is not None:
         claim_id = str(claim.get("claim_id", ""))

src/ccma/services/housekeeper.py

@@ -77,6 +77,9 @@ class Housekeeper:
         overrides the configured setting for just this run without changing it
         permanently -- e.g. to recompute one member's full claim history on demand
         after a contribution change, without retroactively billing everyone else."""
+        # The housekeeper exists to write: it refreshes tasks, creates claims and
+        # updates member records. On a read-only store it must not even take its lock.
+        self.repository.assert_writable()
         current_date = today or date.today()
         delay = _non_negative_delay(member_delay)
         effective_settings = (
@@ -189,6 +192,7 @@ class Housekeeper:
             return _open_findings(working["items"])
 
     def delete_task(self, key: str) -> list[HousekeeperFinding]:
+        self.repository.assert_writable()
         selected_key = key.strip()
         if not selected_key:
             raise RepositoryError("Der Task hat keinen gültigen Key.")

src/ccma/services/mail_composition.py

@@ -0,0 +1,110 @@
+from __future__ import annotations
+
+from datetime import datetime
+from email.message import EmailMessage
+from email.policy import SMTP
+from email.utils import format_datetime, make_msgid
+
+from ccma.domain.mail_templates import (
+    MailTemplate,
+    MailTemplateError,
+    render_mail_template,
+    template_spec,
+    validate_block_markers,
+)
+from ccma.domain.models import Member
+from ccma.domain.placeholders import base_placeholder_values
+from ccma.storage.repository import MemberRepository, RepositoryError
+
+
+def template_values(
+    member: Member,
+    organization: dict | None,
+    *,
+    signature: str,
+    created_at: datetime | None = None,
+) -> dict[str, str]:
+    values = base_placeholder_values(member, organization, created_at=created_at)
+    # A mail always opens with a salutation, so an empty first name would read as
+    # "Hallo ," -- every other placeholder may legitimately render empty.
+    values["member.first_name"] = member.first_name.strip() or "Mitglied"
+    values["signature"] = signature.strip()
+    return values
+
+
+def payment_instructions(
+    member: Member,
+    organization: dict | None,
+    *,
+    due_date: str,
+    reference: str,
+    expect_transfer: bool = False,
+) -> str:
+    """Ready-made payment paragraph: members with an active mandate are told the
+    money is collected, everyone else gets the club's bank details. `expect_transfer`
+    overrides that for a claim the mandate no longer covers -- a dunned claim is
+    expected as a transfer even though the member still has a mandate."""
+    organization = organization if isinstance(organization, dict) else {}
+    if member.mandate_active and not expect_transfer:
+        mandate = member.mandate_reference.strip()
+        mandate_hint = f" (Mandatsreferenz {mandate})" if mandate else ""
+        return (
+            f"Du hast uns ein SEPA-Lastschriftmandat erteilt{mandate_hint} – wir ziehen den "
+            "Betrag fristgerecht von deinem Konto ein. Du musst also nichts weiter tun; "
+            "vor dem Einzug informieren wir dich rechtzeitig per E-Mail."
+        )
+    deadline = f" bis zum {due_date}" if due_date else ""
+    lines = [f"Bitte überweise den Betrag{deadline} auf unser Vereinskonto:", ""]
+    lines.append(f"IBAN: {str(organization.get('iban', '')).strip()}")
+    bic = str(organization.get("bic", "")).strip()
+    if bic:
+        lines.append(f"BIC: {bic}")
+    if reference.strip():
+        lines.append(f"Verwendungszweck: {reference.strip()}")
+    return "\n".join(lines)
+
+
+def render_template(
+    repository: MemberRepository,
+    key: str,
+    values: dict[str, str],
+    repeats: dict[str, list[dict[str, str]]] | None = None,
+) -> MailTemplate:
+    template = repository.get_mail_template(key)
+    try:
+        # The templates are plain files in the store and may have been edited outside
+        # CCMA, so the structural check runs again here: refusing to send beats
+        # sending a mail with "{{#claims}}" in its text.
+        validate_block_markers(key, template.subject, template.body)
+        return render_mail_template(template, values, repeats)
+    except MailTemplateError as exc:
+        raise RepositoryError(
+            f"Die E-Mail-Vorlage „{template_spec(key).label}“ ist fehlerhaft: {exc}"
+        ) from exc
+
+
+def compose_mail(
+    *,
+    recipient: str,
+    subject: str,
+    body: str,
+    sender_name: str,
+    sender_email: str,
+    created_at: datetime | None = None,
+) -> bytes:
+    if not recipient.strip():
+        raise RepositoryError("Für das Mitglied ist keine E-Mail-Adresse hinterlegt.")
+    if not sender_email.strip() or "@" not in sender_email:
+        raise RepositoryError("Für den Versand ist eine gültige Absenderadresse erforderlich.")
+    timestamp = created_at or datetime.now().astimezone()
+    message = EmailMessage(policy=SMTP)
+    message["Message-ID"] = make_msgid(domain=sender_email.rsplit("@", 1)[-1])
+    message["Date"] = format_datetime(timestamp)
+    message["From"] = f"{sender_name.strip()} <{sender_email.strip()}>"
+    message["To"] = recipient.strip()
+    message["Subject"] = subject.strip()
+    message["X-Mozilla-Draft-Info"] = (
+        "internal/draft; vcard=0; receipt=0; DSN=0; uuencode=0; attachmentreminder=0"
+    )
+    message.set_content(body.strip() + "\n", charset="utf-8")
+    return message.as_bytes()

src/ccma/services/member_data_mail.py

@@ -0,0 +1,349 @@
+from __future__ import annotations
+
+import hashlib
+import re
+from contextlib import nullcontext
+from dataclasses import dataclass
+from datetime import date, datetime
+from pathlib import Path
+
+from ccma.domain.dates import format_date_for_display
+from ccma.domain.models import (
+    MEMBERSHIP_STATUS_LABELS,
+    PAYMENT_FREQUENCY_LABELS,
+    Member,
+)
+from ccma.services.mail_composition import compose_mail, render_template, template_values
+from ccma.services.mail_delivery import (
+    append_message,
+    ensure_imap_folder,
+    imap_session,
+    send_via_smtp,
+    smtp_session,
+)
+from ccma.storage.repository import MemberRepository, RepositoryError
+
+# Everyone the club still has a live relationship with. An ended membership is not
+# asked to check data the club is about to delete anyway, and an application has not
+# been decided on yet -- both can still be picked by hand in the dialog.
+DEFAULT_RECIPIENT_STATUSES: tuple[str, ...] = (
+    "accepted_pending_payment",
+    "active",
+    "suspended_contribution",
+    "resigned_end_of_year",
+    "honorary",
+)
+
+# A field the member is meant to complete reads better as a visible gap than as an
+# empty line the eye skips over.
+NOT_STORED = "(nicht hinterlegt)"
+
+# Only makes sense next to a masked IBAN, so it is filled per member rather than
+# written into the template as a fixed line. It sits directly under the record and
+# reads as a footnote to it, which is also why it carries its own parentheses: a
+# dropped line must not leave a blank one behind.
+IBAN_HINT = (
+    "(Die IBAN zeigen wir absichtlich nur verkürzt an – die letzten vier Stellen "
+    "genügen zum Abgleich.)"
+)
+
+
+@dataclass(frozen=True, slots=True)
+class GeneratedDataReviewMail:
+    member_id: str
+    recipient: str
+    # None for "send"/"drafts" delivery -- see reminder_mail.GeneratedReminderMail.
+    export_path: Path | None
+    archive_path: Path
+
+
+def _safe_filename(value: str) -> str:
+    cleaned = re.sub(r"[^A-Za-z0-9._-]+", "-", value.strip()).strip("-._")
+    return cleaned or "Mitglied"
+
+
+def _available_path(directory: Path, filename: str) -> Path:
+    candidate = directory / filename
+    if not candidate.exists():
+        return candidate
+    stem, suffix = Path(filename).stem, Path(filename).suffix
+    index = 2
+    while (directory / f"{stem}-{index}{suffix}").exists():
+        index += 1
+    return directory / f"{stem}-{index}{suffix}"
+
+
+def mask_iban(iban: str) -> str:
+    """Shows enough of the IBAN to recognise the account (country code and the last
+    four digits) without putting the full account number into an e-mail: the member
+    only has to confirm it is still the right account."""
+    cleaned = iban.replace(" ", "").strip()
+    if len(cleaned) < 8:
+        return cleaned
+    return f"{cleaned[:2]}{'*' * (len(cleaned) - 6)}{cleaned[-4:]}"
+
+
+def member_data_fields(member: Member) -> list[tuple[str, str]]:
+    """The stored record as the member gets to see it: label and value, in the order
+    they read naturally. Bank details are only listed for members who have any --
+    asking someone who pays by transfer to check a mandate they never gave is noise."""
+    fields: list[tuple[str, str]] = [
+        ("Mitgliedsnummer", member.member_number),
+        ("Name", " ".join(part for part in (member.first_name, member.last_name) if part)),
+        ("Nickname", member.nickname),
+        ("Geburtsdatum", format_date_for_display(member.birth_date)),
+        ("E-Mail", member.email),
+        ("Telefon", member.phone),
+        ("Straße und Hausnummer", member.street),
+    ]
+    if member.address_addition.strip():
+        fields.append(("Adresszusatz", member.address_addition))
+    fields.extend(
+        [
+            (
+                "PLZ und Ort",
+                " ".join(part for part in (member.postal_code, member.city) if part),
+            ),
+            ("Land", member.country),
+            ("Mitgliedsstatus", MEMBERSHIP_STATUS_LABELS.get(member.status, member.status)),
+            ("Mitglied seit", format_date_for_display(member.membership_started_at)),
+            (
+                "Zahlweise",
+                PAYMENT_FREQUENCY_LABELS.get(
+                    member.payment_frequency, member.payment_frequency
+                ).capitalize(),
+            ),
+        ]
+    )
+    if has_bank_details(member):
+        signed = format_date_for_display(member.mandate_signed_at)
+        fields.extend(
+            [
+                ("Kontoinhaber", member.account_holder),
+                ("IBAN", mask_iban(member.iban)),
+                ("Mandatsreferenz", member.mandate_reference),
+                (
+                    "Lastschriftmandat",
+                    ("aktiv" if member.mandate_active else "nicht aktiv")
+                    + (f", erteilt am {signed}" if signed else ""),
+                ),
+            ]
+        )
+    return [(label, value.strip() or NOT_STORED) for label, value in fields]
+
+
+def has_bank_details(member: Member) -> bool:
+    """Whether the club stores anything about this member's account at all. Members
+    who pay by transfer have nothing here, and asking them to check a mandate they
+    never gave is noise."""
+    return any(
+        value.strip() for value in (member.iban, member.mandate_reference, member.account_holder)
+    )
+
+
+def payment_reference(member: Member) -> str:
+    """What the member should write on a transfer. Both halves are offered because
+    either one identifies the payment on its own: a member who has forgotten their
+    number can fall back on the name, and a name shared by two members is told apart
+    by the number."""
+    return " – ".join(
+        part
+        for part in (
+            member.member_number.strip(),
+            " ".join(value for value in (member.first_name, member.last_name) if value).strip(),
+        )
+        if part
+    )
+
+
+def data_review_recipients(
+    repository: MemberRepository, *, statuses: tuple[str, ...] | None = None
+) -> list[Member]:
+    """The members a data-review run is meant for by default -- an e-mail address is
+    required, so members without one are left out here and reported by the dialog."""
+    wanted = set(statuses if statuses is not None else DEFAULT_RECIPIENT_STATUSES)
+    return [
+        member
+        for member in repository.list_members()
+        if member.status in wanted and member.email.strip()
+    ]
+
+
+def data_review_mail_bytes(
+    repository: MemberRepository,
+    *,
+    member: Member,
+    organization: dict,
+    sender_name: str,
+    sender_email: str,
+    signature: str,
+    created_at: datetime | None = None,
+) -> bytes:
+    values = template_values(member, organization, signature=signature, created_at=created_at)
+    fields = member_data_fields(member)
+    entries = [{"field.label": label, "field.value": value} for label, value in fields]
+    values.update(
+        {
+            "member.iban_masked": mask_iban(member.iban),
+            "data.sheet": "\n".join(f"{label}: {value}" for label, value in fields),
+            "data.count": str(len(fields)),
+            "data.iban_hint": IBAN_HINT if has_bank_details(member) else "",
+            "payment.reference": payment_reference(member),
+        }
+    )
+    rendered = render_template(repository, "data_review", values, {"data": entries})
+    return compose_mail(
+        recipient=member.email,
+        subject=rendered.subject,
+        body=rendered.body,
+        sender_name=sender_name,
+        sender_email=sender_email,
+        created_at=created_at,
+    )
+
+
+def generate_data_review_mails(
+    repository: MemberRepository,
+    member_ids: list[str],
+    *,
+    delivery_mode: str,
+    output_directory: Path | str | None = None,
+    sender_name: str,
+    sender_email: str,
+    signature: str,
+    today: date | None = None,
+) -> tuple[list[GeneratedDataReviewMail], list[str]]:
+    """Sends one data-review mail per member. A member whose mail fails is reported as
+    a warning and the run continues: a single bad address must not stop a mailing to
+    the whole club halfway through."""
+    repository.assert_writable()
+    output: Path | None = None
+    email_settings: dict | None = None
+    smtp_ctx = nullcontext(None)
+    imap_ctx = nullcontext(None)
+    if delivery_mode == "local":
+        if not output_directory:
+            raise RepositoryError("Kein Zielordner für die lokale Ablage angegeben.")
+        output = Path(output_directory)
+        output.mkdir(parents=True, exist_ok=True)
+    elif delivery_mode == "send":
+        email_settings = repository.get_email_settings()
+        smtp_ctx = smtp_session(email_settings)
+        if email_settings["imap_sent_enabled"]:
+            imap_ctx = imap_session(email_settings)
+    elif delivery_mode == "drafts":
+        email_settings = repository.get_email_settings()
+        imap_ctx = imap_session(email_settings)
+    else:
+        raise RepositoryError(f"Unbekannter Versandmodus: {delivery_mode}")
+
+    organization = repository.get_configuration().get("organization") or {}
+    stamp = (today or date.today()).isoformat()
+    generated: list[GeneratedDataReviewMail] = []
+    warnings: list[str] = []
+    # One connection for the whole run -- this mailing covers every member, so
+    # reconnecting per recipient would be slow and invites provider rate limits.
+    with smtp_ctx as smtp_client, imap_ctx as imap_client:
+        if delivery_mode == "drafts":
+            ensure_imap_folder(imap_client, email_settings["imap_drafts_folder"])
+        elif delivery_mode == "send" and imap_client is not None:
+            ensure_imap_folder(imap_client, email_settings["imap_sent_folder"])
+        for member_id in member_ids:
+            try:
+                member = repository.get_member(member_id)
+            except RepositoryError as exc:
+                warnings.append(f"{member_id}: {exc}")
+                continue
+            label = member.member_number or member.display_name
+            if not member.email.strip():
+                warnings.append(f"{label}: E-Mail-Adresse fehlt.")
+                continue
+            export_path: Path | None = None
+            archive_path: Path | None = None
+            # Once this mail has left the building, a later archiving failure must not
+            # hide that it went out, nor abort the members that come after it.
+            delivered = False
+            archive_failure: Exception | None = None
+            try:
+                content = data_review_mail_bytes(
+                    repository,
+                    member=member,
+                    organization=organization,
+                    sender_name=sender_name,
+                    sender_email=sender_email,
+                    signature=signature,
+                )
+                filename = f"Datenpruefung-{stamp}-{_safe_filename(label)}.eml"
+                archive_dir = (
+                    repository.members_root
+                    / member.member_id
+                    / "files"
+                    / "documents"
+                    / "Datenpruefung"
+                )
+                archive_dir.mkdir(parents=True, exist_ok=True)
+                archive_path = _available_path(archive_dir, filename)
+                if delivery_mode == "local":
+                    export_path = _available_path(output, filename)
+                    export_path.write_bytes(content)
+                    delivered = True
+                elif delivery_mode == "send":
+                    send_via_smtp(smtp_client, content)
+                    delivered = True
+                    if imap_client is not None:
+                        append_message(
+                            imap_client,
+                            content,
+                            folder=email_settings["imap_sent_folder"],
+                            flags=r"(\Seen)",
+                        )
+                else:
+                    append_message(
+                        imap_client,
+                        content,
+                        folder=email_settings["imap_drafts_folder"],
+                        flags=r"(\Draft)",
+                    )
+                    delivered = True
+                archive_path.write_bytes(content)
+            except (OSError, RepositoryError) as exc:
+                if not delivered:
+                    if export_path is not None:
+                        export_path.unlink(missing_ok=True)
+                    warnings.append(f"{label}: {exc}")
+                    continue
+                warnings.append(
+                    f"{label}: E-Mail wurde versandt/abgelegt, konnte aber nicht archiviert "
+                    f"werden ({exc}); bitte manuell prüfen."
+                )
+                archive_failure = exc
+
+            digest = hashlib.sha256(content).hexdigest()
+            references: dict[str, str] = {}
+            if archive_failure is None:
+                references["document"] = archive_path.relative_to(
+                    repository.members_root / member.member_id / "files"
+                ).as_posix()
+            data = {
+                "sha256": digest,
+                "recipient": member.email,
+                "delivery_mode": delivery_mode,
+                "field_count": len(member_data_fields(member)),
+            }
+            if archive_failure is not None:
+                data["archive_error"] = str(archive_failure)
+            repository.append_event(
+                member.member_id,
+                event_type="data_review_email_sent",
+                summary="Bitte um Datenüberprüfung verschickt",
+                actor_type="user",
+                actor_name="Vorstand",
+                references=references,
+                data=data,
+            )
+            generated.append(
+                GeneratedDataReviewMail(
+                    member.member_id, member.email, export_path, archive_path
+                )
+            )
+    return generated, warnings

src/ccma/services/reminder_mail.py

@@ -6,13 +6,17 @@ import re
 from contextlib import nullcontext
 from dataclasses import dataclass
 from datetime import datetime
-from email.message import EmailMessage
-from email.policy import SMTP
-from email.utils import format_datetime, make_msgid
 from pathlib import Path
 
-from ccma.domain.contributions import claim_balance
+from ccma.domain.contributions import claim_balance, claim_total, money_text, reminder_items_total
 from ccma.domain.dates import format_date_for_display
+from ccma.domain.models import Member
+from ccma.services.mail_composition import (
+    compose_mail,
+    payment_instructions,
+    render_template,
+    template_values,
+)
 from ccma.services.mail_delivery import (
     append_message,
     ensure_imap_folder,
@@ -49,9 +53,9 @@ def _available_path(directory: Path, filename: str) -> Path:
 
 
 def reminder_mail_bytes(
+    repository: MemberRepository,
     *,
-    recipient: str,
+    member: Member,
-    first_name: str,
     reminder: dict,
     claim: dict,
     balance: str,
@@ -61,62 +65,72 @@ def reminder_mail_bytes(
     signature: str,
     created_at: datetime | None = None,
 ) -> bytes:
-    if not recipient.strip():
+    values = template_values(member, organization, signature=signature, created_at=created_at)
-        raise RepositoryError("Für das Mitglied ist keine E-Mail-Adresse hinterlegt.")
-    if not sender_email.strip() or "@" not in sender_email:
-        raise RepositoryError("Für die Mahnung ist eine gültige Absenderadresse erforderlich.")
-    timestamp = created_at or datetime.now().astimezone()
-    message = EmailMessage(policy=SMTP)
-    message["Message-ID"] = make_msgid(domain=sender_email.rsplit("@", 1)[-1])
-    message["Date"] = format_datetime(timestamp)
-    message["From"] = f"{sender_name.strip()} <{sender_email.strip()}>"
-    message["To"] = recipient.strip()
-    message["Subject"] = f"{reminder.get('name', 'Zahlungserinnerung')} – {claim.get('title', '')}"
-    message["X-Mozilla-Draft-Info"] = (
-        "internal/draft; vcard=0; receipt=0; DSN=0; uuencode=0; attachmentreminder=0"
-    )
-    iban = str(organization.get("iban", "")).strip()
-    bic = str(organization.get("bic", "")).strip()
-    payment_details = f"IBAN: {iban}" + (f"\nBIC: {bic}" if bic else "")
     detail = str(reminder.get("detail", "")).strip()
     fee_items = reminder.get("items") or []
-    fee_lines = (
+    due_date = format_date_for_display(str(claim.get("due_date", "")))
-        "\n".join(
+    payment_deadline = format_date_for_display(str(reminder.get("payment_deadline", "")))
+    reference = " – ".join(
+        part
+        for part in (
+            f"Mitgliedsnummer {member.member_number}" if member.member_number else "",
+            str(claim.get("title", "")).strip(),
+        )
+        if part
+    )
+    values.update(
+        {
+            "claim.title": str(claim.get("title", "")),
+            "claim.description": str(claim.get("description", "") or claim.get("title", "")),
+            "claim.due_date": due_date,
+            "claim.amount": money_text(claim_total(claim)),
+            "claim.balance": balance,
+            "reminder.name": str(reminder.get("name", "Zahlungserinnerung")),
+            "reminder.level": str(reminder.get("level", "")),
+            "reminder.payment_deadline": payment_deadline,
+            "reminder.detail": detail,
+            "reminder.hint": f"Hinweis: {detail}" if detail else "",
+            "reminder.items": "\n".join(
                 f"{item.get('description', 'Gebühr')}: {item.get('amount', '0.00')} Euro"
                 for item in fee_items
-        )
-        if fee_items
-        else "Mahngebühr: 0.00 Euro"
-    )
-    message.set_content(
-        "\n".join(
-            (
-                f"Hallo {first_name.strip() or 'Mitglied'},",
-                "",
-                f"zu der Forderung „{claim.get('title', 'Offene Forderung')}“ "
-                "ist noch ein Betrag offen.",
-                "",
-                f"Offener Betrag: {balance} Euro",
-                f"Ursprünglich fällig: "
-                f"{format_date_for_display(str(claim.get('due_date', '')))}",
-                f"Neue Zahlungsfrist: "
-                f"{format_date_for_display(str(reminder.get('payment_deadline', '')))}",
-                fee_lines,
-                f"Hinweis: {detail}" if detail else "",
-                "",
-                "Bitte überweise den offenen Betrag unter Angabe deiner Mitgliedsnummer an:",
-                payment_details,
-                "",
-                "Sollte sich deine Zahlung mit dieser Nachricht überschnitten haben, "
-                "betrachte sie bitte als gegenstandslos.",
-                "",
-                "Viele Grüße",
-                signature.strip(),
-            )
             ),
-        charset="utf-8",
+            "reminder.fee_total": money_text(reminder_items_total(reminder)),
+            "payment.reference": reference,
+            # A dunning mail only goes out because the money did not arrive, so it
+            # asks for a transfer even from a member with an active mandate: this
+            # claim has left the direct-debit run and telling them "we collect it,
+            # you need not do anything" would contradict the letter it carries.
+            "payment.instructions": payment_instructions(
+                member,
+                organization,
+                due_date=payment_deadline,
+                reference=reference,
+                expect_transfer=True,
+            ),
+        }
+    )
+    rendered = render_template(
+        repository,
+        "reminder",
+        values,
+        {
+            "reminder.items": [
+                {
+                    "item.description": str(item.get("description", "")),
+                    "item.amount": str(item.get("amount", "0.00")),
+                }
+                for item in fee_items
+            ]
+        },
+    )
+    return compose_mail(
+        recipient=member.email,
+        subject=rendered.subject,
+        body=rendered.body,
+        sender_name=sender_name,
+        sender_email=sender_email,
+        created_at=created_at,
     )
-    return message.as_bytes()
 
 
 def generate_and_send_reminder_mail(
@@ -133,6 +147,7 @@ def generate_and_send_reminder_mail(
 ) -> GeneratedReminderMail:
     if delivery_mode not in {"local", "send", "drafts"}:
         raise RepositoryError(f"Unbekannter Versandmodus: {delivery_mode}")
+    repository.assert_writable()
     member = repository.get_member(member_id)
     data, claim = repository.get_claim(member_id, claim_id)
     reminder = repository._find_reminder(data, claim_id, reminder_id)
@@ -167,8 +182,8 @@ def generate_and_send_reminder_mail(
         updated_data, updated_claim = repository.get_claim(member_id, claim_id)
         organization = repository.get_configuration().get("organization") or {}
         content = reminder_mail_bytes(
-            recipient=member.email,
+            repository,
-            first_name=member.first_name,
+            member=member,
             reminder=sent_reminder,
             claim=updated_claim,
             balance=f"{claim_balance(updated_data, updated_claim):.2f}",

src/ccma/services/sepa.py

@@ -12,7 +12,7 @@ from pathlib import Path
 from typing import Any
 from uuid import uuid4
 
-from ccma.domain.contributions import claim_balance
+from ccma.domain.contributions import claim_balance, claim_was_dunned
 from ccma.storage.repository import MemberRepository, RepositoryError, validate_iban
 
 PAIN_NAMESPACE = "urn:iso:std:iso:20022:tech:xsd:pain.008.001.08"
@@ -63,6 +63,7 @@ def pending_direct_debits(
     for member in repository.list_members():
         if not member.mandate_active:
             continue
+        member_label = member.member_number or member.display_name
         missing = [
             label
             for value, label in (
@@ -73,13 +74,13 @@ def pending_direct_debits(
             if not str(value).strip()
         ]
         if missing:
-            warnings.append(f"{member.member_number or member.display_name}: {', '.join(missing)} fehlt.")
+            warnings.append(f"{member_label}: {', '.join(missing)} fehlt.")
             continue
         try:
             validate_iban(member.iban)
             date.fromisoformat(member.mandate_signed_at)
         except (RepositoryError, ValueError) as exc:
-            warnings.append(f"{member.member_number or member.display_name}: {exc}")
+            warnings.append(f"{member_label}: {exc}")
             continue
         data = repository.get_contributions(member.member_id)
         selected = []
@@ -92,7 +93,20 @@ def pending_direct_debits(
             except ValueError:
                 continue
             balance = claim_balance(data, claim)
-            if (due_from is None or claim_due >= due_from) and claim_due <= due_until and balance > 0:
+            if not ((due_from is None or claim_due >= due_from) and claim_due <= due_until):
+                continue
+            if balance <= 0:
+                continue
+            if claim_was_dunned(data, claim):
+                # The debit for this claim already bounced and the member was dunned:
+                # the letter told them to transfer the money themselves, so collecting
+                # it behind their back would contradict it (and can bounce again, with
+                # another fee). Reverting the sent reminder puts it back in the run.
+                warnings.append(
+                    f"{member_label}: „{claim.get('title') or 'Forderung'}“ wurde bereits "
+                    "gemahnt – Zahlung per Überweisung erwartet, kein erneuter Einzug."
+                )
+                continue
             selected.append(claim)
             amount += balance
         if not selected:

src/ccma/services/sepa_mail.py

@@ -5,11 +5,10 @@ import re
 from contextlib import nullcontext
 from dataclasses import dataclass
 from datetime import date, datetime
-from email.message import EmailMessage
-from email.policy import SMTP
-from email.utils import format_datetime, make_msgid
 from pathlib import Path
 
+from ccma.domain.models import Member
+from ccma.services.mail_composition import compose_mail, render_template, template_values
 from ccma.services.mail_delivery import (
     append_message,
     ensure_imap_folder,
@@ -47,55 +46,35 @@ def _available_path(directory: Path, filename: str) -> Path:
 
 
 def debit_mail_bytes(
+    repository: MemberRepository,
     *,
-    recipient: str,
+    member: Member,
-    first_name: str,
     debit: DirectDebit,
     collection_date: date,
-    creditor_id: str,
+    organization: dict,
     sender_name: str,
     sender_email: str,
     signature: str,
     created_at: datetime | None = None,
 ) -> bytes:
-    if not recipient.strip():
+    values = template_values(member, organization, signature=signature, created_at=created_at)
-        raise RepositoryError("Für das Mitglied ist keine E-Mail-Adresse hinterlegt.")
+    values.update(
-    if not sender_email.strip() or "@" not in sender_email:
+        {
-        raise RepositoryError("Für die Info-Mails ist eine gültige Absenderadresse erforderlich.")
+            "debit.amount": f"{debit.amount:.2f}",
-    timestamp = created_at or datetime.now().astimezone()
+            "debit.collection_date": collection_date.strftime("%d.%m.%Y"),
-    message = EmailMessage(policy=SMTP)
+            "debit.purpose": debit.purpose,
-    message["Message-ID"] = make_msgid(domain=sender_email.rsplit("@", 1)[-1])
+            "debit.mandate_reference": debit.mandate_reference,
-    message["Date"] = format_datetime(timestamp)
+        }
-    message["From"] = f"{sender_name.strip()} <{sender_email.strip()}>"
-    message["To"] = recipient.strip()
-    message["Subject"] = f"SEPA-Lastschrift C3MA – {collection_date.strftime('%d.%m.%Y')}"
-    message["X-Mozilla-Draft-Info"] = (
-        "internal/draft; vcard=0; receipt=0; DSN=0; uuencode=0; attachmentreminder=0"
     )
-    greeting = first_name.strip() or "Mitglied"
+    rendered = render_template(repository, "sepa", values)
-    message.set_content(
+    return compose_mail(
-        "\n".join(
+        recipient=member.email,
-            (
+        subject=rendered.subject,
-                f"Hallo {greeting},",
+        body=rendered.body,
-                "",
+        sender_name=sender_name,
-                "hiermit informieren wir dich, dass wir den folgenden Betrag per "
+        sender_email=sender_email,
-                "SEPA-Lastschrift einziehen werden:",
+        created_at=created_at,
-                "",
-                f"Betrag: {debit.amount:.2f} Euro",
-                f"Einzugsdatum: {collection_date.strftime('%d.%m.%Y')}",
-                f"Verwendungszweck: {debit.purpose}",
-                f"Mandatsreferenz: {debit.mandate_reference}",
-                f"Gläubiger-Identifikationsnummer: {creditor_id}",
-                "",
-                "Sollten die Angaben nicht stimmen, melde dich bitte zeitnah bei uns.",
-                "",
-                "Viele Grüße",
-                signature.strip(),
     )
-        ),
-        charset="utf-8",
-    )
-    return message.as_bytes()
 
 
 def generate_debit_mails(
@@ -109,6 +88,7 @@ def generate_debit_mails(
     sender_email: str,
     signature: str,
 ) -> tuple[list[GeneratedDebitMail], list[str]]:
+    repository.assert_writable()
     output: Path | None = None
     email_settings: dict | None = None
     smtp_ctx = nullcontext(None)
@@ -159,11 +139,11 @@ def generate_debit_mails(
             archive_failure: Exception | None = None
             try:
                 content = debit_mail_bytes(
-                    recipient=member.email,
+                    repository,
-                    first_name=member.first_name,
+                    member=member,
                     debit=debit,
                     collection_date=collection_date,
-                    creditor_id=creditor_id,
+                    organization=organization,
                     sender_name=sender_name,
                     sender_email=sender_email,
                     signature=signature,

src/ccma/services/welcome_mail.py

@@ -0,0 +1,272 @@
+from __future__ import annotations
+
+import hashlib
+import os
+from contextlib import nullcontext
+from dataclasses import dataclass
+from datetime import date, datetime
+from decimal import Decimal
+from pathlib import Path
+
+from ccma.domain.contributions import claim_balance, claim_status, claim_total, money_text
+from ccma.domain.dates import format_date_for_display
+from ccma.domain.models import Member
+from ccma.services.mail_composition import (
+    compose_mail,
+    payment_instructions,
+    render_template,
+    template_values,
+)
+from ccma.services.mail_delivery import (
+    append_message,
+    ensure_imap_folder,
+    imap_session,
+    send_via_smtp,
+    smtp_session,
+)
+from ccma.storage.repository import MemberRepository, RepositoryError
+
+OPEN_CLAIM_STATUSES = {"open", "partially_paid", "overdue"}
+
+
+@dataclass(frozen=True, slots=True)
+class GeneratedWelcomeMail:
+    # None for "send"/"drafts" delivery -- see reminder_mail.GeneratedReminderMail.
+    export_path: Path | None
+    archive_path: Path
+    sha256: str
+
+
+def open_claims(repository: MemberRepository, member_id: str) -> list[dict]:
+    """The claims a welcome mail can bill: everything still owed, which for a fresh
+    member is the admission fee plus the first contribution claim(s)."""
+    data = repository.get_contributions(member_id)
+    selected = [
+        claim for claim in data.claims if claim_status(data, claim) in OPEN_CLAIM_STATUSES
+    ]
+    return sorted(selected, key=lambda claim: (str(claim.get("due_date", "")), str(claim.get("title", ""))))
+
+
+def membership_start(member: Member, *, today: date | None = None) -> date:
+    """The date the membership (and with it the first contribution) starts. A member
+    accepted this month usually starts on the 1st of the next one, and that date
+    cannot be stored yet -- "Mitglied seit" rejects future dates."""
+    try:
+        return date.fromisoformat(str(member.membership_started_at))
+    except ValueError:
+        pass
+    try:
+        reference = date.fromisoformat(str(member.accepted_at))
+    except ValueError:
+        reference = today or date.today()
+    return date(reference.year + reference.month // 12, reference.month % 12 + 1, 1)
+
+
+def welcome_mail_bytes(
+    repository: MemberRepository,
+    *,
+    member: Member,
+    claims: list[dict],
+    balances: dict[str, Decimal],
+    organization: dict,
+    sender_name: str,
+    sender_email: str,
+    signature: str,
+    created_at: datetime | None = None,
+) -> bytes:
+    values = template_values(member, organization, signature=signature, created_at=created_at)
+    entries = [
+        {
+            "claim.title": str(claim.get("title", "")),
+            "claim.description": str(claim.get("description", "") or claim.get("title", "")),
+            "claim.due_date": format_date_for_display(str(claim.get("due_date", ""))),
+            "claim.amount": money_text(claim_total(claim)),
+            "claim.balance": money_text(balances[str(claim.get("claim_id", ""))]),
+        }
+        for claim in claims
+    ]
+    total = sum((balances[str(claim.get("claim_id", ""))] for claim in claims), Decimal("0"))
+    due_dates = sorted(
+        str(claim.get("due_date", "")) for claim in claims if str(claim.get("due_date", ""))
+    )
+    first_due_date = format_date_for_display(due_dates[0]) if due_dates else ""
+    reference = " – ".join(
+        part
+        for part in (
+            f"Mitgliedsnummer {member.member_number}" if member.member_number else "",
+            "Mitgliedsbeitrag",
+        )
+        if part
+    )
+    values.update(
+        {
+            "membership.start_date": format_date_for_display(
+                membership_start(member).isoformat()
+            ),
+            "claims.list": "\n".join(
+                f"{entry['claim.description']} (fällig {entry['claim.due_date']}): "
+                f"{entry['claim.balance']} Euro"
+                for entry in entries
+            ),
+            "claims.total": money_text(total),
+            "claims.count": str(len(entries)),
+            "claims.first_due_date": first_due_date,
+            "payment.reference": reference,
+            "payment.instructions": payment_instructions(
+                member, organization, due_date=first_due_date, reference=reference
+            ),
+        }
+    )
+    rendered = render_template(repository, "welcome", values, {"claims": entries})
+    return compose_mail(
+        recipient=member.email,
+        subject=rendered.subject,
+        body=rendered.body,
+        sender_name=sender_name,
+        sender_email=sender_email,
+        created_at=created_at,
+    )
+
+
+def generate_and_send_welcome_mail(
+    repository: MemberRepository,
+    member_id: str,
+    *,
+    claim_ids: list[str] | None = None,
+    delivery_mode: str,
+    output_path: Path | str | None = None,
+    sender_name: str,
+    sender_email: str,
+    signature: str,
+) -> GeneratedWelcomeMail:
+    if delivery_mode not in {"local", "send", "drafts"}:
+        raise RepositoryError(f"Unbekannter Versandmodus: {delivery_mode}")
+    # The mail is archived in the member file, so a read-only store rules the whole
+    # path out -- said here, before anything is rendered or handed to a mail server.
+    repository.assert_writable()
+    member = repository.get_member(member_id)
+    if not member.email.strip():
+        raise RepositoryError("Für das Mitglied ist keine E-Mail-Adresse hinterlegt.")
+    data = repository.get_contributions(member_id)
+    selected_ids = None if claim_ids is None else {str(value) for value in claim_ids}
+    claims = [
+        claim
+        for claim in open_claims(repository, member_id)
+        if selected_ids is None or str(claim.get("claim_id", "")) in selected_ids
+    ]
+    if selected_ids is not None and len(claims) != len(selected_ids):
+        raise RepositoryError("Mindestens eine ausgewählte Forderung ist nicht mehr offen.")
+    balances = {
+        str(claim.get("claim_id", "")): claim_balance(data, claim) for claim in claims
+    }
+    target: Path | None = None
+    if delivery_mode == "local":
+        if not output_path:
+            raise RepositoryError("Kein Zielpfad für die lokale Ablage angegeben.")
+        target = Path(output_path)
+        target.parent.mkdir(parents=True, exist_ok=True)
+        if target.exists():
+            raise RepositoryError(f"Die Ausgabedatei existiert bereits: {target}")
+    organization = repository.get_configuration().get("organization") or {}
+    content = welcome_mail_bytes(
+        repository,
+        member=member,
+        claims=claims,
+        balances=balances,
+        organization=organization,
+        sender_name=sender_name,
+        sender_email=sender_email,
+        signature=signature,
+    )
+    export_path: Path | None = None
+    archive_path: Path | None = None
+    archive_temp: Path | None = None
+    # Same rule as the dunning/SEPA mails: once the mail has reached the SMTP server,
+    # the IMAP folder or the local export file, a later archiving failure must not
+    # hide that it went out -- the event is written either way and the archiving
+    # problem is reported afterwards.
+    delivered = False
+    archive_failure: Exception | None = None
+    try:
+        archive_dir = repository.members_root / member_id / "files" / "documents" / "Willkommen"
+        archive_dir.mkdir(parents=True, exist_ok=True)
+        archive_path = _available_path(archive_dir, f"{date.today().isoformat()}-Willkommen.eml")
+        archive_temp = archive_path.with_name(f".{archive_path.name}.tmp")
+        archive_temp.write_bytes(content)
+        if delivery_mode == "local":
+            export_temp = target.with_name(f".{target.name}.tmp")
+            try:
+                export_temp.write_bytes(content)
+                os.replace(export_temp, target)
+            finally:
+                export_temp.unlink(missing_ok=True)
+            export_path = target
+            delivered = True
+        elif delivery_mode == "send":
+            settings = repository.get_email_settings()
+            sent_copy = imap_session(settings) if settings["imap_sent_enabled"] else nullcontext(None)
+            with smtp_session(settings) as smtp_client, sent_copy as imap_client:
+                send_via_smtp(smtp_client, content)
+                delivered = True
+                if imap_client is not None:
+                    ensure_imap_folder(imap_client, settings["imap_sent_folder"])
+                    append_message(
+                        imap_client, content, folder=settings["imap_sent_folder"], flags=r"(\Seen)"
+                    )
+        else:
+            settings = repository.get_email_settings()
+            with imap_session(settings) as client:
+                ensure_imap_folder(client, settings["imap_drafts_folder"])
+                append_message(
+                    client, content, folder=settings["imap_drafts_folder"], flags=r"(\Draft)"
+                )
+                delivered = True
+        os.replace(archive_temp, archive_path)
+    except Exception as exc:
+        if archive_temp is not None:
+            archive_temp.unlink(missing_ok=True)
+        if not delivered:
+            raise
+        archive_failure = exc
+
+    digest = hashlib.sha256(content).hexdigest()
+    references: dict[str, str] = {}
+    if archive_failure is None:
+        references["document"] = archive_path.relative_to(
+            repository.members_root / member_id / "files"
+        ).as_posix()
+    event_data = {
+        "recipient": member.email,
+        "sha256": digest,
+        "claim_ids": [str(claim.get("claim_id", "")) for claim in claims],
+        "delivery_mode": delivery_mode,
+    }
+    if archive_failure is not None:
+        event_data["archive_error"] = str(archive_failure)
+    repository.append_event(
+        member_id,
+        event_type="welcome_email_sent",
+        summary="Willkommens- und Erstrechnungsmail erzeugt",
+        actor_type="user",
+        actor_name="Vorstand",
+        references=references,
+        data=event_data,
+    )
+    if archive_failure is not None:
+        raise RepositoryError(
+            "Die Willkommensmail wurde zugestellt bzw. abgelegt, konnte aber nicht "
+            f"vollständig archiviert werden: {archive_failure}. Bitte die Mitgliedsakte "
+            "manuell prüfen."
+        ) from archive_failure
+    return GeneratedWelcomeMail(export_path, archive_path, digest)
+
+
+def _available_path(directory: Path, filename: str) -> Path:
+    candidate = directory / filename
+    if not candidate.exists():
+        return candidate
+    stem, suffix = Path(filename).stem, Path(filename).suffix
+    index = 2
+    while (directory / f"{stem}-{index}{suffix}").exists():
+        index += 1
+    return directory / f"{stem}-{index}{suffix}"

src/ccma/storage/atomic.py

@@ -63,6 +63,20 @@ def write_json_atomic(path: Path, data: Any) -> None:
         temporary.unlink(missing_ok=True)
 
 
+def write_text_atomic(path: Path, content: str) -> None:
+    path.parent.mkdir(parents=True, exist_ok=True)
+    descriptor, temporary_name = tempfile.mkstemp(prefix=f".{path.name}.", suffix=".tmp", dir=path.parent)
+    temporary = Path(temporary_name)
+    try:
+        with os.fdopen(descriptor, "w", encoding="utf-8", newline="\n") as handle:
+            handle.write(content)
+            handle.flush()
+            os.fsync(handle.fileno())
+        os.replace(temporary, path)
+    finally:
+        temporary.unlink(missing_ok=True)
+
+
 def read_json(path: Path) -> Any:
     with path.open("r", encoding="utf-8") as handle:
         return json.load(handle)

src/ccma/storage/repository.py

@@ -35,6 +35,16 @@ from ccma.domain.dates import (
     parse_month_input,
     validate_member_dates,
 )
+from ccma.domain.mail_templates import (
+    MAIL_TEMPLATES,
+    MailTemplate,
+    MailTemplateError,
+    default_mail_template,
+    parse_mail_template,
+    serialize_mail_template,
+    template_spec,
+    validate_mail_template,
+)
 from ccma.domain.models import (
     ASSET_CUSTODY_TYPE_LABELS,
     ASSET_OWNER_TYPE_LABELS,
@@ -46,13 +56,24 @@ from ccma.domain.models import (
     Event,
     Member,
 )
-from ccma.storage.atomic import json_content_hash_matches, read_json, write_json_atomic
+from ccma.storage.atomic import (
+    json_content_hash_matches,
+    read_json,
+    write_json_atomic,
+    write_text_atomic,
+)
 
 
 class RepositoryError(RuntimeError):
     pass
 
 
+class ReadOnlyStoreError(RepositoryError):
+    """Raised instead of a bare PermissionError when the store is mounted read-only:
+    the encrypted volume holding the member data can be mounted without write access,
+    and CCMA stays usable for reading in that case."""
+
+
 DEFAULT_MEMBER_NUMBER_PATTERN = "CCMA-{number:04d}"
 
 DEFAULT_CONTRIBUTION_RULES = [
@@ -167,8 +188,60 @@ class MemberRepository:
         self.root = Path(root).expanduser().resolve()
         self.members_root = self.root / "members"
         self.assets_root = self.root / "assets"
+        self._read_only: bool | None = None
+
+    @property
+    def read_only(self) -> bool:
+        """Whether the store can be written to at all. Probed once and cached: the
+        answer only changes when the volume is remounted, which needs a restart (or
+        an explicit refresh_read_only()) anyway."""
+        if self._read_only is None:
+            self._read_only = self.detect_read_only()
+        return self._read_only
+
+    def refresh_read_only(self) -> bool:
+        self._read_only = self.detect_read_only()
+        return self._read_only
+
+    def detect_read_only(self) -> bool:
+        # Probe by actually writing: permissions, mount options and filesystem state
+        # all matter, and only an attempt covers them together. A store directory that
+        # does not exist yet counts as writable when its nearest existing parent is --
+        # that is an ordinary first start, not a read-only volume.
+        target = self.root
+        while not target.exists() and target != target.parent:
+            target = target.parent
+        probe = target / f".ccma-write-probe-{uuid4().hex}"
+        try:
+            probe.touch()
+            probe.unlink()
+        except OSError:
+            return True
+        return False
+
+    def assert_writable(self) -> None:
+        if self.read_only:
+            raise ReadOnlyStoreError(
+                "Der Mitglieder-Store ist schreibgeschützt eingebunden. Änderungen sind "
+                "erst wieder möglich, wenn der Store mit Schreibrechten eingebunden ist."
+            )
+
+    def _write_json(self, path: Path, data) -> None:
+        self.assert_writable()
+        write_json_atomic(path, data)
 
     def initialize(self) -> None:
+        # A read-only store cannot be set up -- but it also does not need to be, as
+        # long as it was initialized while it was still writable. Opening one that was
+        # never initialized is the only case that has to fail here.
+        if self.read_only:
+            if not (self.root / "repository.json").is_file():
+                raise ReadOnlyStoreError(
+                    f"Der Mitglieder-Store {self.root} ist schreibgeschützt eingebunden und "
+                    "enthält keine repository.json. Ein neuer Store kann nur mit "
+                    "Schreibrechten angelegt werden."
+                )
+            return
         self.members_root.mkdir(parents=True, exist_ok=True)
         self.assets_root.mkdir(parents=True, exist_ok=True)
         (self.root / "rules").mkdir(parents=True, exist_ok=True)
@@ -183,9 +256,21 @@ class MemberRepository:
                 destination = templates_root / destination_name
                 if source.is_file() and not destination.exists():
                     shutil.copyfile(source, destination)
+        mail_templates_root = self.mail_templates_root
+        mail_templates_root.mkdir(parents=True, exist_ok=True)
+        for spec in MAIL_TEMPLATES:
+            destination = mail_templates_root / spec.filename
+            if not destination.exists():
+                try:
+                    template = default_mail_template(spec.key)
+                    write_text_atomic(
+                        destination, serialize_mail_template(template.subject, template.body)
+                    )
+                except (MailTemplateError, OSError):
+                    continue
         config_path = self.root / "repository.json"
         if not config_path.exists():
-            write_json_atomic(config_path, DEFAULT_CONFIGURATION)
+            self._write_json(config_path, DEFAULT_CONFIGURATION)
 
     def validate(self) -> list[str]:
         errors: list[str] = []
@@ -376,6 +461,7 @@ class MemberRepository:
             selected_number = self._allocate_member_number(
                 policy["pattern"], policy["allocation_strategy"]
             )
+        self.assert_writable()
         member_id = str(uuid4())
         directory = self._member_path(member_id)
         directory.mkdir(parents=True, exist_ok=False)
@@ -391,8 +477,8 @@ class MemberRepository:
             birth_date=birth_date,
             application_date=application_date,
         )
-        write_json_atomic(directory / "member.json", member.to_dict())
+        self._write_json(directory / "member.json", member.to_dict())
-        write_json_atomic(directory / "contributions.json", ContributionData().to_dict())
+        self._write_json(directory / "contributions.json", ContributionData().to_dict())
         self.append_event(
             member_id,
             event_type="member_created",
@@ -440,7 +526,7 @@ class MemberRepository:
             self._assert_member_number_available(member.member_number, exclude_member_id=member.member_id)
         changes = self._summarize_changes(existing, member)
         member.updated_at = datetime.now().astimezone().isoformat(timespec="seconds")
-        write_json_atomic(self._member_path(member.member_id) / "member.json", member.to_dict())
+        self._write_json(self._member_path(member.member_id) / "member.json", member.to_dict())
         if changes:
             self.append_event(
                 member.member_id,
@@ -501,6 +587,7 @@ class MemberRepository:
         if deposit_amount < 0:
             raise RepositoryError("Die Kaution darf nicht negativ sein.")
         self._validate_asset_relationships(owner_type, owner_member_id, owner_name, custody_type, "")
+        self.assert_writable()
         asset_id = str(uuid4())
         directory = self._asset_path(asset_id)
         directory.mkdir(parents=True, exist_ok=False)
@@ -522,7 +609,7 @@ class MemberRepository:
             condition=condition.strip(),
             estimated_value=estimated_value.strip(),
         )
-        write_json_atomic(directory / "asset.json", asset.to_dict())
+        self._write_json(directory / "asset.json", asset.to_dict())
         self.append_asset_event(
             asset.asset_id,
             event_type="asset_created",
@@ -585,7 +672,7 @@ class MemberRepository:
             raise RepositoryError("Status issued benötigt ein zugeordnetes Mitglied.")
         changes = self._summarize_asset_changes(existing, asset)
         asset.updated_at = datetime.now().astimezone().isoformat(timespec="seconds")
-        write_json_atomic(self._asset_path(asset.asset_id) / "asset.json", asset.to_dict())
+        self._write_json(self._asset_path(asset.asset_id) / "asset.json", asset.to_dict())
         if changes:
             self.append_asset_event(
                 asset.asset_id,
@@ -625,7 +712,7 @@ class MemberRepository:
         asset.custody_type = "member"
         asset.status = "issued"
         asset.updated_at = datetime.now().astimezone().isoformat(timespec="seconds")
-        write_json_atomic(self._asset_path(asset.asset_id) / "asset.json", asset.to_dict())
+        self._write_json(self._asset_path(asset.asset_id) / "asset.json", asset.to_dict())
         self.append_asset_event(
             asset.asset_id,
             event_type="asset_issued",
@@ -653,7 +740,7 @@ class MemberRepository:
         asset.custody_type = "club"
         asset.status = "available"
         asset.updated_at = datetime.now().astimezone().isoformat(timespec="seconds")
-        write_json_atomic(self._asset_path(asset.asset_id) / "asset.json", asset.to_dict())
+        self._write_json(self._asset_path(asset.asset_id) / "asset.json", asset.to_dict())
         self.append_asset_event(
             asset.asset_id,
             event_type="asset_returned",
@@ -812,6 +899,7 @@ class MemberRepository:
             references=references or {},
             data=data or {},
         )
+        self.assert_writable()
         path = directory / "events.jsonl"
         line = json.dumps(event.to_dict(), ensure_ascii=False, separators=(",", ":")) + "\n"
         with path.open("a", encoding="utf-8", newline="\n") as handle:
@@ -867,7 +955,7 @@ class MemberRepository:
 
     def save_contributions(self, member_id: str, data: ContributionData) -> None:
         self.get_member(member_id)
-        write_json_atomic(self._member_path(member_id) / "contributions.json", data.to_dict())
+        self._write_json(self._member_path(member_id) / "contributions.json", data.to_dict())
 
     def get_claim(self, member_id: str, claim_id: str) -> tuple[ContributionData, dict]:
         data = self.get_contributions(member_id)
@@ -2390,6 +2478,7 @@ class MemberRepository:
             references=references or {},
             data=data or {},
         )
+        self.assert_writable()
         path = directory / "events.jsonl"
         line = json.dumps(event.to_dict(), ensure_ascii=False, separators=(",", ":")) + "\n"
         with path.open("a", encoding="utf-8", newline="\n") as handle:
@@ -2496,12 +2585,12 @@ class MemberRepository:
     def refresh_member_record_hashes(self, member_id: str) -> None:
         member = self.get_member(member_id)
         contributions = self.get_contributions(member_id)
-        write_json_atomic(self._member_path(member_id) / "member.json", member.to_dict())
+        self._write_json(self._member_path(member_id) / "member.json", member.to_dict())
-        write_json_atomic(self._member_path(member_id) / "contributions.json", contributions.to_dict())
+        self._write_json(self._member_path(member_id) / "contributions.json", contributions.to_dict())
 
     def refresh_asset_record_hashes(self, asset_id: str) -> None:
         asset = self.get_asset(asset_id)
-        write_json_atomic(self._asset_path(asset_id) / "asset.json", asset.to_dict())
+        self._write_json(self._asset_path(asset_id) / "asset.json", asset.to_dict())
 
     def get_member_number_policy(self) -> dict[str, str]:
         try:
@@ -2538,7 +2627,7 @@ class MemberRepository:
             "allocation_strategy": allocation_strategy,
         }
         config.setdefault("member_number_sequences", {})
-        write_json_atomic(self.root / "repository.json", config)
+        self._write_json(self.root / "repository.json", config)
 
     def get_reminder_policy(self) -> dict:
         config = self.get_configuration()
@@ -2626,7 +2715,7 @@ class MemberRepository:
             "levels": normalized_levels,
             "standard_fee_items": normalized_items,
         }
-        write_json_atomic(self.root / "repository.json", config)
+        self._write_json(self.root / "repository.json", config)
 
     def get_email_settings(self) -> dict:
         config = self.get_configuration()
@@ -2720,7 +2809,45 @@ class MemberRepository:
             "imap_sent_enabled": bool(imap_sent_enabled),
             "imap_sent_folder": imap_sent_folder.strip() or "INBOX.Sent",
         }
-        write_json_atomic(self.root / "repository.json", config)
+        self._write_json(self.root / "repository.json", config)
+
+    @property
+    def mail_templates_root(self) -> Path:
+        return self.root / "templates" / "mail"
+
+    def get_mail_template(self, key: str) -> MailTemplate:
+        """Reads the store's copy of a mail template. Stores created before mail
+        templates existed (or with a deleted file) fall back to the shipped default
+        and get the file written back, so the board always has an editable copy -- on a
+        read-only store the fallback is simply used without storing it."""
+        spec = template_spec(key)
+        path = self.mail_templates_root / spec.filename
+        try:
+            return parse_mail_template(path.read_text(encoding="utf-8"))
+        except OSError:
+            template = default_mail_template(key)
+            try:
+                path.parent.mkdir(parents=True, exist_ok=True)
+                write_text_atomic(path, serialize_mail_template(template.subject, template.body))
+            except OSError:
+                pass
+            return template
+
+    def save_mail_template(self, key: str, *, subject: str, body: str) -> None:
+        self.assert_writable()
+        spec = template_spec(key)
+        try:
+            validate_mail_template(key, subject, body)
+        except MailTemplateError as exc:
+            raise RepositoryError(str(exc)) from exc
+        path = self.mail_templates_root / spec.filename
+        path.parent.mkdir(parents=True, exist_ok=True)
+        write_text_atomic(path, serialize_mail_template(subject, body))
+
+    def reset_mail_template(self, key: str) -> MailTemplate:
+        template = default_mail_template(key)
+        self.save_mail_template(key, subject=template.subject, body=template.body)
+        return template
 
     def save_organization(self, values: dict[str, str]) -> None:
         organization = {key: str(value).strip() for key, value in values.items()}
@@ -2732,7 +2859,7 @@ class MemberRepository:
             raise RepositoryError("Der Vereinsname ist erforderlich.")
         config = self.get_configuration()
         config["organization"] = organization
-        write_json_atomic(self.root / "repository.json", config)
+        self._write_json(self.root / "repository.json", config)
 
     def preview_member_number(
         self, pattern: str | None = None, allocation_strategy: str | None = None
@@ -2778,7 +2905,7 @@ class MemberRepository:
             sequences = {}
             config["member_number_sequences"] = sequences
         sequences[pattern] = next_value
-        write_json_atomic(self.root / "repository.json", config)
+        self._write_json(self.root / "repository.json", config)
         return member_number
 
     def _next_available_member_number(
@@ -2804,6 +2931,7 @@ class MemberRepository:
 
     @contextmanager
     def _member_number_lock(self):
+        self.assert_writable()
         lock_path = self.root / ".member-number.lock"
         lock_path.parent.mkdir(parents=True, exist_ok=True)
         with lock_path.open("a+", encoding="utf-8") as handle:

src/ccma/ui/asset_tab.py

@@ -404,7 +404,11 @@ class AssetTab(ttk.Frame):
         self._confirm_integrity_and_then(self._refresh_hashes_only)
 
     def _refresh_hashes_only(self) -> None:
+        try:
             self.repository.refresh_asset_record_hashes(self.asset_id)
+        except RepositoryError as exc:
+            messagebox.showerror("Prüfsummen konnten nicht erneuert werden", str(exc), parent=self)
+            return
         self.refresh()
         self.on_changed()
 

src/ccma/ui/data_review_mail_dialog.py

@@ -0,0 +1,278 @@
+from __future__ import annotations
+
+import tkinter as tk
+from collections.abc import Callable
+from email.parser import BytesParser
+from email.policy import default as default_policy
+from tkinter import filedialog, messagebox, ttk
+
+from ccma.domain.models import MEMBERSHIP_STATUS_LABELS, Member
+from ccma.services.member_data_mail import (
+    data_review_mail_bytes,
+    data_review_recipients,
+    generate_data_review_mails,
+)
+from ccma.storage.repository import MemberRepository, RepositoryError
+from ccma.ui.email_delivery_dialog import resolve_delivery_mode
+
+
+class DataReviewMailDialog(tk.Toplevel):
+    """Asks the members to check the data the club stores about them. Unlike the
+    other mails this one goes out to everybody at once, so the recipients are picked
+    from a list every member appears in -- with the active ones preselected."""
+
+    def __init__(
+        self,
+        master: tk.Misc,
+        repository: MemberRepository,
+        on_sent: Callable[[], None] | None = None,
+    ):
+        super().__init__(master)
+        self.repository = repository
+        self.on_sent = on_sent
+        self.members: list[Member] = []
+        organization = repository.get_configuration().get("organization") or {}
+        self.sender_name_var = tk.StringVar(value=str(organization.get("name") or "Verwaltung C3MA"))
+        self.sender_email_var = tk.StringVar(value=str(organization.get("email") or ""))
+        self.summary_var = tk.StringVar()
+        self.warning_var = tk.StringVar()
+        self.title("Datenüberprüfung anfragen")
+        self.transient(master.winfo_toplevel())
+        self.geometry("940x620")
+        self.minsize(760, 480)
+        self._build_ui()
+        self._refresh_members()
+        self.after_idle(self.grab_set)
+
+    def _build_ui(self) -> None:
+        self.columnconfigure(0, weight=1)
+        self.rowconfigure(3, weight=1)
+        ttk.Label(
+            self,
+            text=(
+                "Bittet die ausgewählten Mitglieder, die über sie gespeicherten Daten zu "
+                "prüfen. Jede Mail listet den Datensatz genau eines Mitglieds auf; die IBAN "
+                "erscheint dabei nur mit den letzten vier Stellen. Betreff und Text stammen "
+                "aus der Vorlage unter Optionen → E-Mail-Vorlagen."
+            ),
+            wraplength=880,
+        ).grid(row=0, column=0, sticky="w", padx=14, pady=(14, 8))
+        ttk.Label(
+            self,
+            text=(
+                "Vorausgewählt sind alle aktiven Mitgliedschaften mit E-Mail-Adresse – "
+                "einzelne mit Strg+Klick ab- oder zusätzlich auswählen."
+            ),
+            style="Muted.TLabel",
+            wraplength=880,
+        ).grid(row=1, column=0, sticky="w", padx=14, pady=(0, 8))
+        ttk.Label(self, textvariable=self.summary_var, style="Mono.TLabel").grid(
+            row=2, column=0, sticky="w", padx=14, pady=(0, 6)
+        )
+        table = ttk.Frame(self)
+        table.grid(row=3, column=0, sticky="nsew", padx=14)
+        table.columnconfigure(0, weight=1)
+        table.rowconfigure(0, weight=1)
+        self.table = ttk.Treeview(
+            table,
+            columns=("number", "name", "status", "email"),
+            show="headings",
+            selectmode="extended",
+        )
+        for key, title, width, stretch in (
+            ("number", "Nummer", 90, False),
+            ("name", "Name", 220, True),
+            ("status", "Status", 200, False),
+            ("email", "E-Mail", 260, True),
+        ):
+            self.table.heading(key, text=title)
+            self.table.column(key, width=width, anchor="w", stretch=stretch)
+        self.table.grid(row=0, column=0, sticky="nsew")
+        scroll = ttk.Scrollbar(table, orient="vertical", command=self.table.yview)
+        scroll.grid(row=0, column=1, sticky="ns")
+        self.table.configure(yscrollcommand=scroll.set)
+        self.table.bind("<<TreeviewSelect>>", lambda _event: self._update_summary())
+
+        fields = ttk.Frame(self)
+        fields.grid(row=4, column=0, sticky="ew", padx=14, pady=(10, 0))
+        fields.columnconfigure(1, weight=1)
+        ttk.Label(fields, text="Absendername").grid(row=0, column=0, sticky="w", pady=5, padx=(0, 12))
+        ttk.Entry(fields, textvariable=self.sender_name_var, width=52).grid(row=0, column=1, sticky="ew")
+        ttk.Label(fields, text="Absenderadresse").grid(row=1, column=0, sticky="w", pady=5, padx=(0, 12))
+        ttk.Entry(fields, textvariable=self.sender_email_var).grid(row=1, column=1, sticky="ew")
+        ttk.Label(fields, text="Signatur").grid(row=2, column=0, sticky="nw", pady=5, padx=(0, 12))
+        self.signature = tk.Text(fields, width=52, height=4, wrap="word")
+        self.signature.grid(row=2, column=1, sticky="ew", pady=5)
+        self.signature.insert("1.0", "Der Vorstand\nChaos Computer Club Mannheim e.V.")
+
+        footer = ttk.Frame(self, padding=14)
+        footer.grid(row=5, column=0, sticky="ew")
+        footer.columnconfigure(0, weight=1)
+        ttk.Label(footer, textvariable=self.warning_var, style="Muted.TLabel", wraplength=520).grid(
+            row=0, column=0, sticky="w"
+        )
+        ttk.Button(footer, text="Abbrechen", command=self.destroy).grid(row=0, column=1, padx=(8, 0))
+        ttk.Button(footer, text="Vorschau", command=self._preview).grid(row=0, column=2, padx=(8, 0))
+        ttk.Button(
+            footer, text="Mails erzeugen", style="Accent.TButton", command=self._generate
+        ).grid(row=0, column=3, padx=(8, 0))
+
+    def _refresh_members(self) -> None:
+        try:
+            self.members = self.repository.list_members()
+            preselected = {
+                member.member_id for member in data_review_recipients(self.repository)
+            }
+        except RepositoryError as exc:
+            messagebox.showerror("Mitglieder konnten nicht gelesen werden", str(exc), parent=self)
+            return
+        self.table.delete(*self.table.get_children())
+        for index, member in enumerate(self.members):
+            self.table.insert(
+                "",
+                "end",
+                iid=str(index),
+                values=(
+                    member.member_number,
+                    member.display_name,
+                    MEMBERSHIP_STATUS_LABELS.get(member.status, member.status),
+                    member.email or "—",
+                ),
+            )
+        self.table.selection_set(
+            [
+                str(index)
+                for index, member in enumerate(self.members)
+                if member.member_id in preselected
+            ]
+        )
+        without_email = [member for member in self.members if not member.email.strip()]
+        self.warning_var.set(
+            f"{len(without_email)} Mitglied(er) ohne E-Mail-Adresse werden übersprungen."
+            if without_email
+            else ""
+        )
+        self._update_summary()
+
+    def _selected_members(self) -> list[Member]:
+        return [self.members[int(iid)] for iid in sorted(self.table.selection(), key=int)]
+
+    def _update_summary(self) -> None:
+        selected = self._selected_members()
+        reachable = [member for member in selected if member.email.strip()]
+        self.summary_var.set(
+            f"{len(selected)} von {len(self.members)} Mitgliedern ausgewählt – "
+            f"{len(reachable)} Mail(s) werden erzeugt"
+        )
+
+    def _preview(self) -> None:
+        selected = self._selected_members()
+        member = next((item for item in selected if item.email.strip()), None)
+        if member is None:
+            messagebox.showinfo(
+                "Keine Vorschau möglich",
+                "Bitte mindestens ein Mitglied mit E-Mail-Adresse auswählen.",
+                parent=self,
+            )
+            return
+        try:
+            content = data_review_mail_bytes(
+                self.repository,
+                member=member,
+                organization=self.repository.get_configuration().get("organization") or {},
+                sender_name=self.sender_name_var.get(),
+                sender_email=self.sender_email_var.get(),
+                signature=self.signature.get("1.0", "end-1c"),
+            )
+        except (OSError, RepositoryError) as exc:
+            messagebox.showerror("Vorschau nicht möglich", str(exc), parent=self)
+            return
+        message = BytesParser(policy=default_policy).parsebytes(content)
+        window = tk.Toplevel(self)
+        window.title(f"Vorschau für {member.display_name}")
+        window.transient(self)
+        window.columnconfigure(0, weight=1)
+        window.rowconfigure(1, weight=1)
+        ttk.Label(window, text=f"Betreff: {message['Subject']}", padding=12).grid(
+            row=0, column=0, sticky="w"
+        )
+        preview = tk.Text(window, wrap="word", width=88, height=30)
+        preview.grid(row=1, column=0, sticky="nsew", padx=12, pady=(0, 12))
+        preview.insert("1.0", message.get_content())
+        preview.configure(state="disabled")
+        scroll = ttk.Scrollbar(window, orient="vertical", command=preview.yview)
+        scroll.grid(row=1, column=1, sticky="ns", pady=(0, 12), padx=(0, 12))
+        preview.configure(yscrollcommand=scroll.set)
+        ttk.Button(window, text="Schließen", command=window.destroy).grid(
+            row=2, column=0, columnspan=2, sticky="e", padx=12, pady=(0, 12)
+        )
+
+    def _generate(self) -> None:
+        recipients = [member for member in self._selected_members() if member.email.strip()]
+        if not recipients:
+            messagebox.showinfo(
+                "Keine Empfänger",
+                "Bitte mindestens ein Mitglied mit E-Mail-Adresse auswählen.",
+                parent=self,
+            )
+            return
+        delivery_mode = resolve_delivery_mode(self, self.repository)
+        if delivery_mode is None:
+            return
+        output_directory = None
+        if delivery_mode == "local":
+            selected = filedialog.askdirectory(
+                parent=self,
+                title="Ausgabeordner für die Thunderbird-Entwürfe auswählen",
+                mustexist=True,
+            )
+            if not selected:
+                return
+            output_directory = selected
+        # A mailing to the whole club cannot be taken back, so the count is confirmed
+        # once more -- especially when "Senden" would put it on the wire right away.
+        action = {
+            "local": "als Datei abgelegt",
+            "send": "sofort versandt",
+            "drafts": "als Entwurf im Postfach abgelegt",
+        }[delivery_mode]
+        if not messagebox.askyesno(
+            "Datenüberprüfung verschicken",
+            f"An {len(recipients)} Mitglied(er) wird je eine Mail mit deren gespeicherten "
+            f"Daten {action}.\n\nJetzt erzeugen?",
+            parent=self,
+        ):
+            return
+        self.configure(cursor="watch")
+        self.update_idletasks()
+        try:
+            generated, warnings = generate_data_review_mails(
+                self.repository,
+                [member.member_id for member in recipients],
+                delivery_mode=delivery_mode,
+                output_directory=output_directory,
+                sender_name=self.sender_name_var.get(),
+                sender_email=self.sender_email_var.get(),
+                signature=self.signature.get("1.0", "end-1c"),
+            )
+        except (OSError, RepositoryError) as exc:
+            messagebox.showerror("Mails konnten nicht erzeugt werden", str(exc), parent=self)
+            return
+        finally:
+            self.configure(cursor="")
+        location = {
+            "local": f"in\n{output_directory}\nerzeugt",
+            "send": "versandt",
+            "drafts": "als Entwurf im Postfach abgelegt",
+        }[delivery_mode]
+        detail = (
+            f"{len(generated)} Mail(s) wurden {location} und in den Mitgliederakten archiviert."
+        )
+        if warnings:
+            detail += "\n\nÜbersprungen:\n" + "\n".join(warnings[:12])
+            if len(warnings) > 12:
+                detail += f"\n… und {len(warnings) - 12} weitere."
+        messagebox.showinfo("Datenüberprüfung verschickt", detail, parent=self)
+        self.destroy()
+        if self.on_sent is not None:
+            self.on_sent()

src/ccma/ui/main_window.py

@@ -10,9 +10,11 @@ from ccma.services.housekeeper import Housekeeper
 from ccma.storage.repository import MemberRepository, RepositoryError
 from ccma.ui.asset_tab import AssetTab
 from ccma.ui.claim_tab import ClaimTab
+from ccma.ui.data_review_mail_dialog import DataReviewMailDialog
 from ccma.ui.dialogs import EditAssetDialog, IssueAssetDialog, NewAssetDialog, NewMemberDialog
 from ccma.ui.icons import IconStore
 from ccma.ui.member_tab import MemberTab
+from ccma.ui.messages import MessageAction, MessageBannerList, TabMessage
 from ccma.ui.options_dialog import OptionsDialog
 from ccma.ui.sepa_dialog import SepaExportDialog
 from ccma.ui.theme import load_theme
@@ -98,10 +100,14 @@ class MainWindow(ttk.Frame):
 
     def _build_ui(self) -> None:
         self.columnconfigure(0, weight=1)
-        self.rowconfigure(1, weight=1)
+        self.rowconfigure(2, weight=1)
         self._build_ribbon()
+        # The read-only notice sits above the tabs rather than inside one, so it stays
+        # visible no matter which member, asset or housekeeper tab is in front.
+        self.messages = MessageBannerList(self)
+        self.messages.grid(row=1, column=0, sticky="ew", pady=(10, 0))
         self.notebook = ttk.Notebook(self)
-        self.notebook.grid(row=1, column=0, sticky="nsew", pady=(10, 0))
+        self.notebook.grid(row=2, column=0, sticky="nsew", pady=(10, 0))
         self.tabs = TabManager(self.notebook)
         self.dashboard = DashboardTab(
             self.notebook,
@@ -117,16 +123,75 @@ class MainWindow(ttk.Frame):
             icon_name="view-dashboard",
         )
         status = ttk.Frame(self, padding=(6, 5))
-        status.grid(row=2, column=0, sticky="ew")
+        status.grid(row=3, column=0, sticky="ew")
         status.columnconfigure(0, weight=1)
         ttk.Label(status, textvariable=self.status_var, style="Status.TLabel").grid(
             row=0, column=0, sticky="w"
         )
-        ttk.Label(
+        self.store_var = tk.StringVar()
-            status,
+        ttk.Label(status, textvariable=self.store_var, style="Status.TLabel").grid(
-            text=f"STORE {self.repository.root}  ·  VERSION {__version__}",
+            row=0, column=1, sticky="e"
-            style="Status.TLabel",
+        )
-        ).grid(row=0, column=1, sticky="e")
+        # Everything that reflects write access is refreshed from one place, so a
+        # store that becomes writable mid-session updates all of it together.
+        self._refresh_store_state()
+
+    def _refresh_store_state(self) -> None:
+        """Window title, status bar and banner all say whether the store can be
+        written to -- they are rebuilt together so none of them can be left behind."""
+        read_only = self.repository.read_only
+        title = f"CCMA · v{__version__}"
+        self.master.title(f"{title} · NUR LESEN (Store schreibgeschützt)" if read_only else title)
+        store_label = f"STORE {self.repository.root}"
+        if read_only:
+            store_label = f"{store_label}  ·  NUR LESEN"
+        self.store_var.set(f"{store_label}  ·  VERSION {__version__}")
+        messages = []
+        if read_only:
+            messages.append(
+                TabMessage(
+                    "warning",
+                    "ACHTUNG: Der Mitglieder-Store ist schreibgeschützt eingebunden. "
+                    "Alle Daten sind nur lesbar – Änderungen, Dokumente, E-Mails und der "
+                    "Hausmeister sind deaktiviert. Den Store mit Schreibrechten einbinden "
+                    "und hier auf „Erneut prüfen“ klicken – ein Neustart ist dafür nicht "
+                    "nötig.",
+                    MessageAction("Erneut prüfen", self._recheck_store_access),
+                )
+            )
+        self.messages.set_messages(messages)
+
+    def _recheck_store_access(self) -> None:
+        """Lets the board remount the volume without restarting first -- if it came
+        back writable, every read-only marker goes away and the housekeeper, skipped
+        at startup, can run right away."""
+        if self.repository.refresh_read_only():
+            self._refresh_store_state()
+            self.status_var.set("Der Store ist weiterhin schreibgeschützt.")
+            return
+        self._refresh_store_state()
+        self.status_var.set("Der Store ist wieder beschreibbar.")
+        # The startup pass was skipped, so the task list is empty rather than current:
+        # offer the run that fills it instead of leaving a misleading dashboard.
+        if messagebox.askyesno(
+            "Store beschreibbar",
+            "Der Mitglieder-Store ist jetzt mit Schreibrechten eingebunden. Der "
+            "Hausmeister wurde beim Start übersprungen, seine Vorgangsliste ist daher "
+            "noch leer.\n\nJetzt einen Hausmeisterlauf starten?",
+            parent=self,
+        ):
+            self.run_housekeeper()
+
+    def _refuse_read_only(self, action: str) -> bool:
+        if not self.repository.read_only:
+            return False
+        messagebox.showwarning(
+            "Store ist schreibgeschützt",
+            f"{action} ist nicht möglich, solange der Mitglieder-Store nur lesend "
+            "eingebunden ist.",
+            parent=self,
+        )
+        return True
 
     def _build_ribbon(self) -> None:
         ribbon = ttk.Frame(self, style="Ribbon.TFrame")
@@ -381,6 +446,7 @@ class MainWindow(ttk.Frame):
             self.findings,
             self.open_member,
             lambda: self.tabs.close(key),
+            self.open_data_review_mail,
         )
         self.tabs.add(
             key,
@@ -416,10 +482,19 @@ class MainWindow(ttk.Frame):
     def open_sepa_export(self) -> None:
         SepaExportDialog(self, self.repository)
 
+    def open_data_review_mail(self) -> None:
+        if self._refuse_read_only("Der Versand der Datenüberprüfung"):
+            return
+        DataReviewMailDialog(self, self.repository)
+
     def new_member(self) -> None:
+        if self._refuse_read_only("Das Anlegen eines Mitglieds"):
+            return
         NewMemberDialog(self, self.repository, self._member_created)
 
     def new_asset(self) -> None:
+        if self._refuse_read_only("Das Anlegen eines Assets"):
+            return
         NewAssetDialog(self, self.repository, self._asset_created)
 
     def _member_created(self, member: Member) -> None:
@@ -499,6 +574,8 @@ class MainWindow(ttk.Frame):
         )
 
     def run_housekeeper(self) -> list[HousekeeperFinding]:
+        if self._refuse_read_only("Ein Hausmeisterlauf"):
+            return self.findings
         self.findings = Housekeeper(self.repository, self.config.housekeeper_settings()).run()
         self.refresh_overview(run_housekeeper=False)
         self.status_var.set(f"Hausmeisterlauf beendet: {len(self.findings)} Vorgänge.")
@@ -507,6 +584,8 @@ class MainWindow(ttk.Frame):
     def run_housekeeper_for_member(
         self, member_id: str, retroactive_claims: bool = False
     ) -> list[HousekeeperFinding]:
+        if self._refuse_read_only("Ein Hausmeisterlauf"):
+            return self.findings
         self.findings = Housekeeper(self.repository, self.config.housekeeper_settings()).run(
             member_id=member_id, retroactive_claims=retroactive_claims or None
         )
@@ -515,13 +594,15 @@ class MainWindow(ttk.Frame):
         return self.findings
 
     def delete_housekeeper_task(self, key: str) -> list[HousekeeperFinding]:
+        if self._refuse_read_only("Das Löschen eines Hausmeister-Tasks"):
+            return self.findings
         self.findings = Housekeeper(self.repository, self.config.housekeeper_settings()).delete_task(key)
         self.refresh_overview(run_housekeeper=False)
         self.status_var.set("Hausmeister-Task gelöscht.")
         return self.findings
 
     def refresh_overview(self, *, run_housekeeper: bool = True) -> None:
-        if run_housekeeper:
+        if run_housekeeper and not self.repository.read_only:
             self.findings = Housekeeper(self.repository, self.config.housekeeper_settings()).run()
         self.dashboard.update_data(self.repository.member_count(), self.findings)
         members_tab = self.tabs.tabs.get("members")

src/ccma/ui/member_tab.py

@@ -38,6 +38,7 @@ from ccma.ui.labels import display_label, storage_key
 from ccma.ui.messages import MessageAction, MessageBannerList, TabMessage
 from ccma.ui.payment_dialog import PaymentCreateDialog, PaymentEditDialog
 from ccma.ui.scrolling import ScrollableFrame
+from ccma.ui.welcome_mail_dialog import WelcomeMailDialog
 
 # Shared column sizing for the ledger-style tables (Forderungen/Zahlungen/Spenden): date-
 # and amount-like columns get the same fixed width, status columns get a third more
@@ -355,6 +356,13 @@ class MemberTab(ttk.Frame):
         self.claims.grid(row=1, column=0, sticky="nsew")
         self.claims.bind("<Double-1>", lambda _event: self._open_selected_claim())
         self.claims.bind("<Return>", lambda _event: self._open_selected_claim())
+        claim_actions = ttk.Frame(contribution_tab)
+        claim_actions.grid(row=2, column=0, sticky="e", pady=(8, 0))
+        ttk.Button(
+            claim_actions,
+            text="Willkommens- und Erstrechnungsmail",
+            command=self._send_welcome_mail,
+        ).pack(side="left")
 
         contribution_override_tab.columnconfigure(0, weight=1)
         contribution_override_tab.rowconfigure(1, weight=1)
@@ -1122,7 +1130,11 @@ class MemberTab(ttk.Frame):
         self._confirm_integrity_and_then(self._refresh_hashes_only)
 
     def _refresh_hashes_only(self) -> None:
+        try:
             self.repository.refresh_member_record_hashes(self.member_id)
+        except RepositoryError as exc:
+            messagebox.showerror("Prüfsummen konnten nicht erneuert werden", str(exc), parent=self)
+            return
         self.refresh()
         self.on_changed()
 
@@ -1142,6 +1154,7 @@ class MemberTab(ttk.Frame):
         text = self.comment_var.get().strip()
         if not text:
             return
+        try:
             self.repository.append_event(
                 self.member_id,
                 event_type="board_comment",
@@ -1149,6 +1162,9 @@ class MemberTab(ttk.Frame):
                 actor_type="user",
                 actor_name="Vorstand",
             )
+        except RepositoryError as exc:
+            messagebox.showerror("Kommentar konnte nicht gespeichert werden", str(exc), parent=self)
+            return
         self.comment_var.set("")
         self._refresh_events()
 
@@ -1177,6 +1193,14 @@ class MemberTab(ttk.Frame):
         except OSError as exc:
             messagebox.showerror("Datei konnte nicht geöffnet werden", str(exc), parent=self)
 
+    def _send_welcome_mail(self) -> None:
+        WelcomeMailDialog(self, self.repository, self.member_id, self._welcome_mail_sent)
+
+    def _welcome_mail_sent(self) -> None:
+        self._refresh_documents()
+        self._refresh_events()
+        self.on_changed()
+
     def _create_document(self) -> None:
         DocumentTemplateDialog(
             self,

src/ccma/ui/options_dialog.py

@@ -7,6 +7,14 @@ from tkinter import filedialog, messagebox, ttk
 
 from ccma.config import AppConfig
 from ccma.domain.contributions import decimal_value, money_text
+from ccma.domain.mail_templates import (
+    MAIL_TEMPLATES,
+    MailTemplateError,
+    default_mail_template,
+    placeholder_entries,
+    template_spec,
+    validate_mail_template,
+)
 from ccma.domain.models import HOUSEKEEPER_MEMBER_FIELD_LABELS
 from ccma.services.intervals import (
     IntervalValidationError,
@@ -67,9 +75,21 @@ class OptionsDialog(tk.Toplevel):
                 "website", "iban", "bic", "creditor_id",
             )
         }
+        # Mail templates are edited one at a time but saved together with the rest of
+        # the options, so the edits of every tab are kept in memory until "Speichern".
+        self.mail_template_key = MAIL_TEMPLATES[0].key
+        self.mail_template_edits: dict[str, tuple[str, str]] = {}
+        self.mail_template_original: dict[str, tuple[str, str]] = {}
+        self.mail_template_var = tk.StringVar(value=MAIL_TEMPLATES[0].label)
+        self.mail_template_subject_var = tk.StringVar()
+        self.mail_template_hint_var = tk.StringVar()
+        self.mail_template_snippets: dict[str, str] = {}
         self.title("Optionen")
         self.transient(master.winfo_toplevel())
-        self.grab_set()
+        # Tk refuses a grab on a window that is not on screen yet ("window not
+        # viewable"), and this dialog builds enough tabs to still be unmapped here --
+        # so the grab waits for the window like it does in the other dialogs.
+        self.after_idle(self.grab_set)
         self.resizable(True, True)
         self._build_ui()
         self.bind("<Escape>", lambda _event: self.destroy())
@@ -102,6 +122,7 @@ class OptionsDialog(tk.Toplevel):
         automation = ttk.Frame(notebook, padding=16)
         reminders = ttk.Frame(notebook, padding=16)
         email = ttk.Frame(notebook, padding=16)
+        mail_templates = ttk.Frame(notebook, padding=16)
         changelog = ChangelogView(notebook)
         notebook.add(paths, text="Pfade")
         notebook.add(appearance, text="Darstellung")
@@ -110,6 +131,7 @@ class OptionsDialog(tk.Toplevel):
         notebook.add(automation, text="Hausmeister")
         notebook.add(reminders, text="Mahnungen")
         notebook.add(email, text="E-Mail-Versand")
+        notebook.add(mail_templates, text="E-Mail-Vorlagen")
         notebook.add(changelog, text="Changelog")
         self._build_paths(paths)
         self._build_appearance(appearance)
@@ -118,6 +140,7 @@ class OptionsDialog(tk.Toplevel):
         self._build_automation(automation)
         self._build_reminders(reminders)
         self._build_email(email)
+        self._build_mail_templates(mail_templates)
 
         buttons = ttk.Frame(root)
         buttons.grid(row=1, column=0, sticky="e", pady=(12, 0))
@@ -891,8 +914,13 @@ class OptionsDialog(tk.Toplevel):
         self.config_obj.optional_member_fields = tuple(
             field for field, variable in self.optional_member_field_vars.items() if variable.get()
         )
+        # Program settings live in the user's config directory and stay writable even
+        # when the member store does not -- so they are saved either way, and only the
+        # store-backed settings are skipped (with a notice) on a read-only store.
+        store_read_only = self.repository.read_only
         try:
             self.config_obj.save()
+            if not store_read_only:
                 self.repository.save_member_number_policy(
                     mode=number_mode,
                     pattern=number_pattern,
@@ -907,13 +935,199 @@ class OptionsDialog(tk.Toplevel):
                     standard_fee_items=self.standard_items,
                 )
                 self.repository.save_email_settings(**email_settings)
+                self._save_mail_templates()
         except (OSError, RepositoryError) as exc:
             messagebox.showerror("Optionen konnten nicht gespeichert werden", str(exc), parent=self)
             return
+        if store_read_only:
+            messagebox.showwarning(
+                "Store ist schreibgeschützt",
+                "Die Programmeinstellungen wurden gespeichert. Vereinsdaten, "
+                "Mitgliedsnummern, Mahnungen, E-Mail-Versand und E-Mail-Vorlagen konnten "
+                "nicht gespeichert werden, weil der Mitglieder-Store nur lesend "
+                "eingebunden ist.",
+                parent=self,
+            )
         if self.on_saved:
             self.on_saved(store_changed)
         self.destroy()
 
+    def _build_mail_templates(self, parent: ttk.Frame) -> None:
+        parent.columnconfigure(0, weight=1)
+        parent.rowconfigure(4, weight=1)
+        ttk.Label(
+            parent,
+            text=(
+                "Die Texte aller vom Programm erzeugten E-Mails liegen als bearbeitbare "
+                "Vorlagen im Mitglieder-Store unter templates/mail/. Platzhalter in doppelten "
+                "geschweiften Klammern werden beim Versand mit den Daten des Mitglieds gefüllt."
+            ),
+            style="Muted.TLabel",
+            wraplength=820,
+        ).grid(row=0, column=0, columnspan=2, sticky="w", pady=(0, 12))
+
+        chooser = ttk.Frame(parent)
+        chooser.grid(row=1, column=0, columnspan=2, sticky="ew")
+        chooser.columnconfigure(1, weight=1)
+        ttk.Label(chooser, text="Vorlage").grid(row=0, column=0, sticky="w", padx=(0, 12))
+        selector = ttk.Combobox(
+            chooser,
+            textvariable=self.mail_template_var,
+            values=[spec.label for spec in MAIL_TEMPLATES],
+            state="readonly",
+            width=32,
+        )
+        selector.grid(row=0, column=1, sticky="w")
+        selector.bind("<<ComboboxSelected>>", lambda _event: self._select_mail_template())
+        ttk.Button(
+            chooser, text="Standardtext wiederherstellen", command=self._reset_mail_template
+        ).grid(row=0, column=2, sticky="e", padx=(12, 0))
+        ttk.Label(
+            parent, textvariable=self.mail_template_hint_var, style="Muted.TLabel", wraplength=820
+        ).grid(row=2, column=0, columnspan=2, sticky="w", pady=(6, 12))
+
+        subject = ttk.Frame(parent)
+        subject.grid(row=3, column=0, columnspan=2, sticky="ew", pady=(0, 8))
+        subject.columnconfigure(1, weight=1)
+        ttk.Label(subject, text="Betreff").grid(row=0, column=0, sticky="w", padx=(0, 12))
+        ttk.Entry(subject, textvariable=self.mail_template_subject_var).grid(
+            row=0, column=1, sticky="ew"
+        )
+
+        editor = ttk.Frame(parent)
+        editor.grid(row=4, column=0, sticky="nsew")
+        editor.columnconfigure(0, weight=1)
+        editor.rowconfigure(0, weight=1)
+        self.mail_template_body = tk.Text(editor, wrap="word", height=16, width=70, undo=True)
+        self.mail_template_body.grid(row=0, column=0, sticky="nsew")
+        body_scroll = ttk.Scrollbar(editor, orient="vertical", command=self.mail_template_body.yview)
+        body_scroll.grid(row=0, column=1, sticky="ns")
+        self.mail_template_body.configure(yscrollcommand=body_scroll.set)
+
+        placeholders = ttk.Frame(parent)
+        placeholders.grid(row=4, column=1, sticky="nsew", padx=(12, 0))
+        placeholders.columnconfigure(0, weight=1)
+        placeholders.rowconfigure(1, weight=1)
+        ttk.Label(placeholders, text="Platzhalter (Doppelklick fügt ein)").grid(
+            row=0, column=0, columnspan=2, sticky="w", pady=(0, 4)
+        )
+        self.mail_template_placeholders = ttk.Treeview(
+            placeholders, columns=("name", "help"), show="headings", selectmode="browse", height=14
+        )
+        for key, title, width in (("name", "Platzhalter", 210), ("help", "Bedeutung", 230)):
+            self.mail_template_placeholders.heading(key, text=title)
+            self.mail_template_placeholders.column(key, width=width, anchor="w", stretch=key == "help")
+        self.mail_template_placeholders.grid(row=1, column=0, sticky="nsew")
+        placeholder_scroll = ttk.Scrollbar(
+            placeholders, orient="vertical", command=self.mail_template_placeholders.yview
+        )
+        placeholder_scroll.grid(row=1, column=1, sticky="ns")
+        self.mail_template_placeholders.configure(yscrollcommand=placeholder_scroll.set)
+        self.mail_template_placeholders.bind(
+            "<Double-1>", lambda _event: self._insert_mail_placeholder()
+        )
+        self.mail_template_placeholders.bind(
+            "<Return>", lambda _event: self._insert_mail_placeholder()
+        )
+        self._load_mail_template(self.mail_template_key)
+
+    def _load_mail_template(self, key: str) -> None:
+        if key not in self.mail_template_edits:
+            try:
+                template = self.repository.get_mail_template(key)
+            except (OSError, RepositoryError) as exc:
+                messagebox.showerror(
+                    "Vorlage konnte nicht geladen werden", str(exc), parent=self
+                )
+                return
+            self.mail_template_edits[key] = (template.subject, template.body)
+            self.mail_template_original[key] = (template.subject, template.body)
+        subject, body = self.mail_template_edits[key]
+        self.mail_template_key = key
+        spec = template_spec(key)
+        self.mail_template_var.set(spec.label)
+        self.mail_template_hint_var.set(f"{spec.description} (Datei: {spec.filename})")
+        self.mail_template_subject_var.set(subject)
+        self.mail_template_body.delete("1.0", "end")
+        self.mail_template_body.insert("1.0", body)
+        self.mail_template_placeholders.delete(*self.mail_template_placeholders.get_children())
+        # The row text is a readable label; what actually gets inserted is the entry's
+        # snippet, which for a repeat block is the whole block and not its description.
+        self.mail_template_snippets = {}
+        for entry in placeholder_entries(key):
+            label = f"    {entry.label}" if entry.indented else entry.label
+            row = self.mail_template_placeholders.insert(
+                "", "end", values=(label, entry.description)
+            )
+            self.mail_template_snippets[row] = entry.snippet
+
+    def _capture_mail_template(self) -> None:
+        if not hasattr(self, "mail_template_body"):
+            return
+        self.mail_template_edits[self.mail_template_key] = (
+            self.mail_template_subject_var.get(),
+            self.mail_template_body.get("1.0", "end-1c"),
+        )
+
+    def _select_mail_template(self) -> None:
+        self._capture_mail_template()
+        label = self.mail_template_var.get()
+        key = next((spec.key for spec in MAIL_TEMPLATES if spec.label == label), None)
+        if key:
+            self._load_mail_template(key)
+
+    def _reset_mail_template(self) -> None:
+        key = self.mail_template_key
+        spec = template_spec(key)
+        if not messagebox.askyesno(
+            "Standardtext wiederherstellen",
+            f"Soll die Vorlage „{spec.label}“ auf den mitgelieferten Standardtext "
+            "zurückgesetzt werden? Deine Änderungen an dieser Vorlage gehen dabei verloren.",
+            parent=self,
+        ):
+            return
+        try:
+            template = default_mail_template(key)
+        except MailTemplateError as exc:
+            messagebox.showerror("Standardtext nicht verfügbar", str(exc), parent=self)
+            return
+        self.mail_template_edits[key] = (template.subject, template.body)
+        self._load_mail_template(key)
+
+    def _insert_mail_placeholder(self) -> None:
+        selected = self.mail_template_placeholders.selection()
+        if not selected:
+            return
+        snippet = self.mail_template_snippets.get(selected[0])
+        if not snippet:
+            return
+        # A multi-line block only works on lines of its own, so it starts on a fresh
+        # one instead of being appended to whatever the cursor sat behind.
+        if "\n" in snippet.strip() and not self._mail_cursor_at_line_start():
+            snippet = "\n" + snippet
+        self.mail_template_body.insert("insert", snippet)
+        self.mail_template_body.focus_set()
+
+    def _mail_cursor_at_line_start(self) -> bool:
+        return str(self.mail_template_body.index("insert")).split(".")[1] == "0"
+
+    def _save_mail_templates(self) -> None:
+        self._capture_mail_template()
+        pending = {
+            key: value
+            for key, value in self.mail_template_edits.items()
+            if self.mail_template_original.get(key) != value
+        }
+        # Check every edited template before writing the first one: a mistake in one
+        # must not leave the others half-saved.
+        for key, (subject, body) in pending.items():
+            try:
+                validate_mail_template(key, subject, body)
+            except MailTemplateError as exc:
+                raise RepositoryError(f"{template_spec(key).label}: {exc}") from exc
+        for key, (subject, body) in pending.items():
+            self.repository.save_mail_template(key, subject=subject, body=body)
+
     def _center_on_parent(self) -> None:
         self.update_idletasks()
         parent = self.master.winfo_toplevel()

src/ccma/ui/sepa_dialog.py

@@ -154,7 +154,9 @@ class SepaExportDialog(tk.Toplevel):
         )
         self._update_summary()
         self.warning_var.set(
-            f"{len(self.warnings)} unvollständige(s) Mandat(e) übersprungen." if self.warnings else ""
+            f"{len(self.warnings)} Position(en) übersprungen – Details beim Export."
+            if self.warnings
+            else ""
         )
 
     def _selected_debits(self) -> list:
@@ -185,7 +187,7 @@ class SepaExportDialog(tk.Toplevel):
             )
             return None
         if self.warnings and not messagebox.askyesno(
-            "Unvollständige Mandate",
+            "Übersprungene Positionen",
             "\n".join(self.warnings[:10]) + "\n\nMit den übrigen Lastschriften fortfahren?",
             parent=self,
         ):

src/ccma/ui/splash.py

@@ -121,7 +121,14 @@ class SplashScreen(tk.Toplevel):
                 self.repository.list_members()
                 member_count = len(self.repository.list_member_ids())
                 findings = []
-                if self.run_housekeeper:
+                # A read-only store makes the housekeeper impossible, not just
+                # unwanted: every one of its passes writes. Skipping it keeps the
+                # rest of the startup -- and the whole read-only session -- working.
+                if self.repository.read_only:
+                    self._messages.put(
+                        ("status", "Store ist schreibgeschützt – Hausmeister übersprungen …")
+                    )
+                elif self.run_housekeeper:
                     self._messages.put(("status", "Starte Hausmeister …"))
                     findings = Housekeeper(self.repository, self.housekeeper_settings).run(
                         member_delay=_member_delay_for_splash(

src/ccma/ui/welcome_mail_dialog.py

@@ -0,0 +1,241 @@
+from __future__ import annotations
+
+import tkinter as tk
+from collections.abc import Callable
+from decimal import Decimal
+from email.parser import BytesParser
+from email.policy import default as default_policy
+from tkinter import filedialog, messagebox, ttk
+
+from ccma.domain.contributions import claim_balance, money_text
+from ccma.domain.dates import format_date_for_display
+from ccma.services.welcome_mail import (
+    generate_and_send_welcome_mail,
+    open_claims,
+    welcome_mail_bytes,
+)
+from ccma.storage.repository import MemberRepository, RepositoryError
+from ccma.ui.email_delivery_dialog import resolve_delivery_mode
+
+
+class WelcomeMailDialog(tk.Toplevel):
+    """Sends the welcome mail that doubles as the first invoice for a new member:
+    membership start, member number and every claim that is still open."""
+
+    def __init__(
+        self,
+        master: tk.Misc,
+        repository: MemberRepository,
+        member_id: str,
+        on_sent: Callable[[], None],
+    ):
+        super().__init__(master)
+        self.repository = repository
+        self.member_id = member_id
+        self.on_sent = on_sent
+        self.claims: list[dict] = []
+        organization = repository.get_configuration().get("organization") or {}
+        self.sender_name_var = tk.StringVar(value=str(organization.get("name") or "Verwaltung C3MA"))
+        self.sender_email_var = tk.StringVar(value=str(organization.get("email") or ""))
+        self.summary_var = tk.StringVar()
+        self.title("Willkommens- und Erstrechnungsmail")
+        self.transient(master.winfo_toplevel())
+        self.resizable(True, True)
+        self._build_ui()
+        self._refresh_claims()
+        self.grab_set()
+
+    def _build_ui(self) -> None:
+        self.columnconfigure(0, weight=1)
+        self.rowconfigure(2, weight=1)
+        ttk.Label(
+            self,
+            text=(
+                "Begrüßt das neue Mitglied und stellt die noch offenen Forderungen "
+                "(Aufnahmegebühr und erster Beitrag) als Erstrechnung zusammen. Text und "
+                "Betreff stammen aus der Vorlage unter Optionen → E-Mail-Vorlagen."
+            ),
+            wraplength=640,
+        ).grid(row=0, column=0, sticky="w", padx=14, pady=(14, 8))
+        ttk.Label(
+            self,
+            text=(
+                "Standardmäßig sind alle offenen Forderungen ausgewählt – einzelne mit "
+                "Strg+Klick abwählen."
+            ),
+            style="Muted.TLabel",
+            wraplength=640,
+        ).grid(row=1, column=0, sticky="w", padx=14, pady=(0, 8))
+        table = ttk.Frame(self)
+        table.grid(row=2, column=0, sticky="nsew", padx=14)
+        table.columnconfigure(0, weight=1)
+        table.rowconfigure(0, weight=1)
+        self.table = ttk.Treeview(
+            table,
+            columns=("due", "amount", "title"),
+            show="headings",
+            selectmode="extended",
+            height=6,
+        )
+        for key, title, width in (
+            ("due", "Fällig", 90),
+            ("amount", "Offen", 90),
+            ("title", "Forderung", 320),
+        ):
+            self.table.heading(key, text=title)
+            self.table.column(key, width=width, anchor="w", stretch=key == "title")
+        self.table.grid(row=0, column=0, sticky="nsew")
+        scroll = ttk.Scrollbar(table, orient="vertical", command=self.table.yview)
+        scroll.grid(row=0, column=1, sticky="ns")
+        self.table.configure(yscrollcommand=scroll.set)
+        self.table.bind("<<TreeviewSelect>>", lambda _event: self._update_summary())
+        ttk.Label(self, textvariable=self.summary_var, style="Mono.TLabel").grid(
+            row=3, column=0, sticky="w", padx=14, pady=(6, 10)
+        )
+
+        fields = ttk.Frame(self)
+        fields.grid(row=4, column=0, sticky="ew", padx=14)
+        fields.columnconfigure(1, weight=1)
+        ttk.Label(fields, text="Absendername").grid(row=0, column=0, sticky="w", pady=5, padx=(0, 12))
+        ttk.Entry(fields, textvariable=self.sender_name_var, width=52).grid(row=0, column=1, sticky="ew")
+        ttk.Label(fields, text="Absenderadresse").grid(row=1, column=0, sticky="w", pady=5, padx=(0, 12))
+        ttk.Entry(fields, textvariable=self.sender_email_var).grid(row=1, column=1, sticky="ew")
+        ttk.Label(fields, text="Signatur").grid(row=2, column=0, sticky="nw", pady=5, padx=(0, 12))
+        self.signature = tk.Text(fields, width=52, height=4, wrap="word")
+        self.signature.grid(row=2, column=1, sticky="ew", pady=5)
+        self.signature.insert("1.0", "Der Vorstand\nChaos Computer Club Mannheim e.V.")
+
+        buttons = ttk.Frame(self, padding=14)
+        buttons.grid(row=5, column=0, sticky="e")
+        ttk.Button(buttons, text="Abbrechen", command=self.destroy).pack(side="left")
+        ttk.Button(buttons, text="Vorschau", command=self._preview).pack(side="left", padx=(8, 0))
+        ttk.Button(
+            buttons, text="E-Mail erzeugen", style="Accent.TButton", command=self._generate
+        ).pack(side="left", padx=(8, 0))
+
+    def _refresh_claims(self) -> None:
+        try:
+            self.claims = open_claims(self.repository, self.member_id)
+            data = self.repository.get_contributions(self.member_id)
+        except RepositoryError as exc:
+            messagebox.showerror("Forderungen konnten nicht gelesen werden", str(exc), parent=self)
+            return
+        self.table.delete(*self.table.get_children())
+        for index, claim in enumerate(self.claims):
+            self.table.insert(
+                "",
+                "end",
+                iid=str(index),
+                values=(
+                    format_date_for_display(str(claim.get("due_date", ""))),
+                    money_text(claim_balance(data, claim)),
+                    str(claim.get("description", "") or claim.get("title", "")),
+                ),
+            )
+        self.table.selection_set(self.table.get_children())
+        self._update_summary()
+
+    def _selected_claims(self) -> list[dict]:
+        return [self.claims[int(iid)] for iid in self.table.selection()]
+
+    def _update_summary(self) -> None:
+        data = self.repository.get_contributions(self.member_id)
+        selected = self._selected_claims()
+        total = sum((claim_balance(data, claim) for claim in selected), Decimal("0"))
+        self.summary_var.set(
+            f"{len(selected)} von {len(self.claims)} Forderungen ausgewählt – "
+            f"Gesamtbetrag {money_text(total)} Euro"
+        )
+
+    def _mail_bytes(self) -> bytes:
+        member = self.repository.get_member(self.member_id)
+        data = self.repository.get_contributions(self.member_id)
+        claims = self._selected_claims()
+        return welcome_mail_bytes(
+            self.repository,
+            member=member,
+            claims=claims,
+            balances={
+                str(claim.get("claim_id", "")): claim_balance(data, claim) for claim in claims
+            },
+            organization=self.repository.get_configuration().get("organization") or {},
+            sender_name=self.sender_name_var.get(),
+            sender_email=self.sender_email_var.get(),
+            signature=self.signature.get("1.0", "end-1c"),
+        )
+
+    def _preview(self) -> None:
+        try:
+            message = BytesParser(policy=default_policy).parsebytes(self._mail_bytes())
+        except (OSError, RepositoryError) as exc:
+            messagebox.showerror("Vorschau nicht möglich", str(exc), parent=self)
+            return
+        window = tk.Toplevel(self)
+        window.title("Vorschau der Willkommensmail")
+        window.transient(self)
+        window.columnconfigure(0, weight=1)
+        window.rowconfigure(1, weight=1)
+        ttk.Label(window, text=f"Betreff: {message['Subject']}", padding=12).grid(
+            row=0, column=0, sticky="w"
+        )
+        preview = tk.Text(window, wrap="word", width=88, height=28)
+        preview.grid(row=1, column=0, sticky="nsew", padx=12, pady=(0, 12))
+        preview.insert("1.0", message.get_content())
+        preview.configure(state="disabled")
+        scroll = ttk.Scrollbar(window, orient="vertical", command=preview.yview)
+        scroll.grid(row=1, column=1, sticky="ns", pady=(0, 12), padx=(0, 12))
+        preview.configure(yscrollcommand=scroll.set)
+        ttk.Button(window, text="Schließen", command=window.destroy).grid(
+            row=2, column=0, columnspan=2, sticky="e", padx=12, pady=(0, 12)
+        )
+
+    def _generate(self) -> None:
+        selected = self._selected_claims()
+        if not selected and not messagebox.askyesno(
+            "Keine Forderung ausgewählt",
+            "Es ist keine Forderung ausgewählt. Soll die Mail ohne Rechnungspositionen "
+            "erzeugt werden?",
+            parent=self,
+        ):
+            return
+        delivery_mode = resolve_delivery_mode(self, self.repository)
+        if delivery_mode is None:
+            return
+        output_path = None
+        if delivery_mode == "local":
+            chosen = filedialog.asksaveasfilename(
+                parent=self,
+                title="Willkommensmail als Thunderbird-Entwurf speichern",
+                defaultextension=".eml",
+                initialfile="Willkommen.eml",
+                filetypes=[("E-Mail-Datei", "*.eml"), ("Alle Dateien", "*.*")],
+            )
+            if not chosen:
+                return
+            output_path = chosen
+        try:
+            result = generate_and_send_welcome_mail(
+                self.repository,
+                self.member_id,
+                claim_ids=[str(claim.get("claim_id", "")) for claim in selected],
+                delivery_mode=delivery_mode,
+                output_path=output_path,
+                sender_name=self.sender_name_var.get(),
+                sender_email=self.sender_email_var.get(),
+                signature=self.signature.get("1.0", "end-1c"),
+            )
+        except (OSError, RepositoryError) as exc:
+            messagebox.showerror("E-Mail konnte nicht erzeugt werden", str(exc), parent=self)
+            return
+        outcome = {
+            "local": f"gespeichert:\n{result.export_path}",
+            "send": "direkt versandt.",
+            "drafts": "als Entwurf im Postfach abgelegt.",
+        }[delivery_mode]
+        messagebox.showinfo(
+            "Willkommensmail erzeugt",
+            f"Die E-Mail wurde {outcome}\n\nEine Kopie liegt in der Mitgliederakte.",
+            parent=self,
+        )
+        self.destroy()
+        self.on_sent()

src/ccma/ui/work_tabs.py

@@ -245,12 +245,14 @@ class MembersTab(ttk.Frame):
         findings: list[HousekeeperFinding],
         on_open: Callable[[str], None],
         on_close: Callable[[], None],
+        on_data_review: Callable[[], None] | None = None,
     ):
         super().__init__(master, padding=12)
         self.members = members
         self.findings = findings
         self.on_open = on_open
         self.on_close = on_close
+        self.on_data_review = on_data_review
         self._build_ui()
 
     def _build_ui(self) -> None:
@@ -262,7 +264,15 @@ class MembersTab(ttk.Frame):
         ttk.Label(header, text="MITGLIEDER", style="TabTitle.TLabel").grid(row=0, column=0, sticky="w")
         self.count_var = tk.StringVar()
         ttk.Label(header, textvariable=self.count_var, style="Mono.TLabel").grid(row=1, column=0, sticky="w")
-        ttk.Button(header, text="Tab schließen", command=self.on_close).grid(row=0, column=1, rowspan=2)
+        buttons = ttk.Frame(header)
+        buttons.grid(row=0, column=1, rowspan=2, sticky="e")
+        if self.on_data_review is not None:
+            # The mailing goes to every member, so it belongs where every member is
+            # listed rather than into the already crowded ribbon.
+            ttk.Button(
+                buttons, text="Datenüberprüfung anfragen", command=self.on_data_review
+            ).pack(side="left", padx=(0, 8))
+        ttk.Button(buttons, text="Tab schließen", command=self.on_close).pack(side="left")
         filters = _filter_label_frame(self)
         filters.grid(row=1, column=0, sticky="ew", pady=(0, 10))
         filter_row = ttk.Frame(filters)

tests/conftest.py

@@ -0,0 +1,20 @@
+import pytest
+
+
+@pytest.fixture(scope="session")
+def tk_root():
+    """One Tk root for the whole test session, shared by every UI test module: the
+    icon library binds its images to the first root, so a second one (or a root torn
+    down between tests) invalidates them with 'image "pyimage1" doesn\'t exist'.
+    Skips where there is no display, which keeps the suite running on headless CI."""
+    tk = pytest.importorskip("tkinter")
+    from ccma.ui.theme import load_theme
+
+    try:
+        root = tk.Tk()
+    except tk.TclError as exc:
+        pytest.skip(f"kein Display verfügbar: {exc}")
+    root.withdraw()
+    load_theme(root, "dark")
+    yield root
+    root.destroy()

tests/test_data_review_mail_ui.py

@@ -0,0 +1,72 @@
+import pytest
+
+pytest.importorskip("tkinter")
+
+from ccma.storage.repository import MemberRepository  # noqa: E402
+
+
+@pytest.fixture
+def repository(tmp_path):
+    repository = MemberRepository(tmp_path / "store")
+    repository.initialize()
+    organization = repository.get_configuration()["organization"]
+    organization.update({"name": "CCC Mannheim e.V.", "email": "verwaltung@example.org"})
+    repository.save_organization(organization)
+    return repository
+
+
+def _member(repository, first_name, last_name, *, email="", status="active"):
+    member = repository.create_member(
+        first_name=first_name, last_name=last_name, birth_date="1990-01-01"
+    )
+    member.email = email
+    member.status = status
+    repository.save_member(member)
+    return member
+
+
+def test_the_dialog_preselects_reachable_live_memberships(tk_root, repository):
+    from ccma.ui.data_review_mail_dialog import DataReviewMailDialog
+
+    _member(repository, "Ada", "Lovelace", email="ada@example.org")
+    _member(repository, "Grace", "Hopper", email="grace@example.org", status="ended")
+    _member(repository, "Anon", "Ymous")
+
+    dialog = DataReviewMailDialog(tk_root, repository)
+    try:
+        tk_root.update()
+        selected = [member.display_name for member in dialog._selected_members()]
+
+        assert selected == ["Ada Lovelace"]
+        # Every member stays listed so a resigned one can still be picked by hand.
+        assert len(dialog.table.get_children()) == 3
+        assert "1 von 3 Mitgliedern ausgewählt" in dialog.summary_var.get()
+        assert "1 Mail(s) werden erzeugt" in dialog.summary_var.get()
+        assert "1 Mitglied(er) ohne E-Mail-Adresse" in dialog.warning_var.get()
+    finally:
+        dialog.destroy()
+        tk_root.update()
+
+
+def test_a_selection_without_an_address_generates_nothing(tk_root, repository, monkeypatch):
+    from tkinter import messagebox
+
+    import ccma.ui.data_review_mail_dialog as module
+
+    _member(repository, "Anon", "Ymous")
+    dialog = module.DataReviewMailDialog(tk_root, repository)
+    try:
+        tk_root.update()
+        dialog.table.selection_set(dialog.table.get_children())
+        informed = []
+        monkeypatch.setattr(messagebox, "showinfo", lambda *args, **kwargs: informed.append(args))
+        monkeypatch.setattr(
+            module, "resolve_delivery_mode", lambda *args: pytest.fail("kein Versand erwartet")
+        )
+
+        dialog._generate()
+
+        assert informed and "Keine Empfänger" in informed[0][0]
+    finally:
+        dialog.destroy()
+        tk_root.update()

tests/test_documents.py

@@ -129,6 +129,7 @@ def test_default_templates_are_seeded_without_overwriting_store_version(tmp_path
         "Forderung mit Positionen.fodt",
         "Mahnung.fodt",
         "Mitglied.fodt",
+        "mail",
     }
 
 

tests/test_mail_templates.py

@@ -0,0 +1,217 @@
+import pytest
+
+from ccma.domain.mail_templates import (
+    MAIL_TEMPLATES,
+    MailTemplate,
+    MailTemplateBlock,
+    MailTemplateError,
+    MailTemplateSpec,
+    default_mail_template,
+    parse_mail_template,
+    placeholder_entries,
+    render_mail_template,
+    serialize_mail_template,
+    validate_block_markers,
+    validate_mail_template,
+)
+from ccma.storage.repository import MemberRepository, RepositoryError
+
+
+def test_subject_header_round_trips_through_file_format() -> None:
+    text = serialize_mail_template("Hallo {{member.first_name}}", "Zeile eins\nZeile zwei")
+
+    template = parse_mail_template(text)
+
+    assert text.startswith("Betreff: Hallo {{member.first_name}}\n\n")
+    assert template == MailTemplate("Hallo {{member.first_name}}", "Zeile eins\nZeile zwei")
+
+
+def test_shipped_defaults_only_use_declared_placeholders() -> None:
+    for spec in MAIL_TEMPLATES:
+        template = default_mail_template(spec.key)
+        validate_mail_template(spec.key, template.subject, template.body)
+
+
+def test_rendering_fills_values_and_expands_repeat_blocks() -> None:
+    template = MailTemplate(
+        "Beitrag für {{member.first_name}}",
+        "Hallo {{member.first_name}},\n"
+        "{{#claims}}- {{claim.title}}: {{claim.amount}}{{/claims}}\n"
+        "Summe: {{claims.total}}",
+    )
+
+    rendered = render_mail_template(
+        template,
+        {"member.first_name": "Ada", "claims.total": "75.00"},
+        {
+            "claims": [
+                {"claim.title": "Aufnahmegebühr", "claim.amount": "15.00"},
+                {"claim.title": "Mitgliedsbeitrag", "claim.amount": "60.00"},
+            ]
+        },
+    )
+
+    assert rendered.subject == "Beitrag für Ada"
+    assert rendered.body == (
+        "Hallo Ada,\n- Aufnahmegebühr: 15.00\n- Mitgliedsbeitrag: 60.00\nSumme: 75.00"
+    )
+
+
+def test_line_holding_only_an_empty_placeholder_is_dropped() -> None:
+    template = MailTemplate("Betreff", "Erste Zeile\n{{reminder.hint}}\nLetzte Zeile")
+
+    assert render_mail_template(template, {"reminder.hint": ""}).body == "Erste Zeile\nLetzte Zeile"
+    assert (
+        render_mail_template(template, {"reminder.hint": "Hinweis: X"}).body
+        == "Erste Zeile\nHinweis: X\nLetzte Zeile"
+    )
+
+
+def test_unknown_placeholder_is_rejected_while_editing() -> None:
+    with pytest.raises(MailTemplateError, match="member.favourite_colour"):
+        validate_mail_template("welcome", "Betreff", "Hallo {{member.favourite_colour}}")
+
+
+def test_store_copies_are_seeded_editable_and_resettable(tmp_path) -> None:
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+    path = repository.mail_templates_root / "willkommen.txt"
+    assert path.is_file()
+
+    repository.save_mail_template("welcome", subject="Moin {{member.first_name}}", body="Kurz und knapp.")
+    assert repository.get_mail_template("welcome") == MailTemplate(
+        "Moin {{member.first_name}}", "Kurz und knapp."
+    )
+    assert "Moin {{member.first_name}}" in path.read_text(encoding="utf-8")
+
+    repository.reset_mail_template("welcome")
+    assert repository.get_mail_template("welcome") == default_mail_template("welcome")
+
+
+def test_missing_template_file_falls_back_to_shipped_default(tmp_path) -> None:
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+    (repository.mail_templates_root / "mahnung.txt").unlink()
+
+    template = repository.get_mail_template("reminder")
+
+    assert template == default_mail_template("reminder")
+    assert (repository.mail_templates_root / "mahnung.txt").is_file()
+
+
+def test_saving_a_broken_template_is_refused(tmp_path) -> None:
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+
+    with pytest.raises(RepositoryError, match="Platzhalter"):
+        repository.save_mail_template("reminder", subject="Mahnung", body="Hallo {{member.nonsense}}")
+    with pytest.raises(RepositoryError, match="Betreff"):
+        repository.save_mail_template("reminder", subject="   ", body="Hallo")
+
+
+def test_block_rows_insert_a_working_block_not_its_description() -> None:
+    entries = placeholder_entries("welcome")
+    block = next(entry for entry in entries if entry.label.startswith("{{#claims}}"))
+
+    # The label may abbreviate the block, the inserted snippet may not.
+    assert block.label == "{{#claims}} … {{/claims}}"
+    assert block.snippet.startswith("{{#claims}}\n")
+    assert block.snippet.rstrip().endswith("{{/claims}}")
+    assert "{{claim.description}}" in block.snippet
+    assert "…" not in block.snippet
+    assert all("…" not in entry.snippet for entry in entries)
+
+
+def test_inserted_block_validates_and_renders_one_line_per_claim() -> None:
+    block = next(
+        entry for entry in placeholder_entries("welcome") if entry.label.startswith("{{#claims}}")
+    )
+    body = f"Hallo {{{{member.first_name}}}},\n\n{block.snippet}\nSumme: {{{{claims.total}}}}"
+
+    validate_mail_template("welcome", "Betreff", body)
+    rendered = render_mail_template(
+        MailTemplate("Betreff", body),
+        {"member.first_name": "Ada", "claims.total": "75.00"},
+        {
+            "claims": [
+                {
+                    "claim.description": "Aufnahmegebühr",
+                    "claim.due_date": "17.09.2026",
+                    "claim.balance": "15.00",
+                },
+                {
+                    "claim.description": "Mitgliedsbeitrag 2. Halbjahr 2026",
+                    "claim.due_date": "17.09.2026",
+                    "claim.balance": "60.00",
+                },
+            ]
+        },
+    )
+
+    assert "Aufnahmegebühr (fällig 17.09.2026): 15.00 Euro" in rendered.body
+    assert "Mitgliedsbeitrag 2. Halbjahr 2026 (fällig 17.09.2026): 60.00 Euro" in rendered.body
+    assert "…" not in rendered.body
+
+
+def test_every_block_snippet_is_valid_in_its_own_template() -> None:
+    for spec in MAIL_TEMPLATES:
+        for block in spec.blocks:
+            validate_mail_template(spec.key, "Betreff", block.snippet)
+
+
+@pytest.mark.parametrize(
+    ("body", "expected"),
+    [
+        ("Hallo\n{{#claims}}\n{{claim.title}}", "wird nicht geschlossen"),
+        ("Hallo\n{{/claims}}\nGruß", "ohne zugehöriges"),
+        ("{{#claims}}\n{{claim.title}}\n{{/claims}}\n{{/claims}}", "ohne zugehöriges"),
+        ("{{#claims}}\n{{#claims}}\nx\n{{/claims}}\n{{/claims}}", "verschachtelt"),
+        ("{{#members}}\nx\n{{/members}}", "Unbekannter Wiederholungsblock"),
+        ("{{ # claims }}\nx", "wird nicht geschlossen"),
+    ],
+)
+def test_unbalanced_repeat_markers_are_rejected(body, expected) -> None:
+    with pytest.raises(MailTemplateError, match=expected):
+        validate_mail_template("welcome", "Betreff", body)
+
+
+def test_repeat_markers_in_the_subject_are_rejected() -> None:
+    with pytest.raises(MailTemplateError, match="Betreff"):
+        validate_mail_template("welcome", "Beitrag {{#claims}}", "Hallo")
+
+
+def test_a_template_without_blocks_rejects_every_marker() -> None:
+    with pytest.raises(MailTemplateError, match="Verfügbar: keine"):
+        validate_mail_template("sepa", "Betreff", "{{#claims}}\nx\n{{/claims}}")
+
+
+def test_a_closing_marker_must_match_the_open_one(monkeypatch) -> None:
+    two_blocks = MailTemplateSpec(
+        key="two-blocks",
+        label="Test",
+        filename="test.txt",
+        description="",
+        placeholders=(),
+        blocks=(
+            MailTemplateBlock("first", "", (("item.a", ""),), "{{item.a}}"),
+            MailTemplateBlock("second", "", (("item.b", ""),), "{{item.b}}"),
+        ),
+    )
+    monkeypatch.setattr("ccma.domain.mail_templates.MAIL_TEMPLATES", (two_blocks,))
+
+    with pytest.raises(MailTemplateError, match="Erwartet wird \\{\\{/first\\}\\}"):
+        validate_block_markers("two-blocks", "Betreff", "{{#first}}\nx\n{{/second}}")
+
+
+def test_a_broken_template_is_not_stored(tmp_path) -> None:
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+    path = repository.mail_templates_root / "willkommen.txt"
+    before = path.read_text(encoding="utf-8")
+
+    with pytest.raises(RepositoryError, match="wird nicht geschlossen"):
+        repository.save_mail_template(
+            "welcome", subject="Willkommen", body="Hallo\n{{#claims}}\n{{claim.title}}"
+        )
+
+    assert path.read_text(encoding="utf-8") == before

tests/test_main_window_ui.py

@@ -0,0 +1,122 @@
+import os
+import stat
+
+import pytest
+
+pytest.importorskip("tkinter")
+
+from ccma.config import AppConfig  # noqa: E402
+from ccma.storage.repository import MemberRepository  # noqa: E402
+
+# Root ignores the permission bits that stand in for a read-only mount here.
+pytestmark = pytest.mark.skipif(
+    hasattr(os, "geteuid") and os.geteuid() == 0, reason="root bypasses file permissions"
+)
+
+
+def _set_writable(root, writable: bool) -> None:
+    for path in sorted(root.rglob("*"), reverse=True) + [root]:
+        mode = stat.S_IMODE(path.stat().st_mode)
+        path.chmod(mode | stat.S_IWUSR if writable else mode & ~stat.S_IWUSR)
+
+
+@pytest.fixture
+def read_only_window(tk_root, tmp_path):
+    from ccma.ui.main_window import MainWindow
+
+    root_path = tmp_path / "store"
+    repository = MemberRepository(root_path)
+    repository.initialize()
+    repository.create_member(first_name="Ada", last_name="Lovelace", birth_date="1990-01-01")
+    _set_writable(root_path, False)
+
+    window = MainWindow(tk_root, MemberRepository(root_path), AppConfig(store_path=str(root_path)), [], [])
+    window.pack(fill="both", expand=True)
+    tk_root.update()
+    yield window
+    window.destroy()
+    tk_root.title("")
+    tk_root.update()
+    _set_writable(root_path, True)
+
+
+def test_a_read_only_store_is_marked_everywhere(read_only_window, tk_root):
+    assert "NUR LESEN" in tk_root.title()
+    assert "NUR LESEN" in read_only_window.store_var.get()
+    assert read_only_window.messages.winfo_manager(), "der Warnbanner fehlt"
+
+
+def test_the_banner_does_not_ask_for_a_restart(read_only_window):
+    banner = read_only_window.messages.winfo_children()[0]
+    text = " ".join(
+        str(child.cget("text"))
+        for child in banner.winfo_children()[0].winfo_children()
+        if "text" in child.keys()
+    )
+    # The banner used to end with "und CCMA neu starten", which is wrong -- the
+    # session recovers in place.
+    assert "Erneut prüfen" in text
+    assert "neu starten" not in text.casefold()
+    assert "Neustart ist dafür nicht nötig" in text
+
+
+def test_the_data_review_mailing_is_refused_on_a_read_only_store(read_only_window, monkeypatch):
+    from tkinter import messagebox
+
+    warned = []
+    monkeypatch.setattr(messagebox, "showwarning", lambda *args, **kwargs: warned.append(args))
+
+    read_only_window.open_data_review_mail()
+
+    assert warned and "schreibgeschützt" in warned[0][0]
+    assert "Der Versand der Datenüberprüfung ist nicht möglich" in warned[0][1]
+    assert not [
+        child
+        for child in read_only_window.winfo_children()
+        if child.winfo_class() == "Toplevel"
+    ]
+
+
+def test_a_remounted_store_clears_every_read_only_marker(read_only_window, tk_root, monkeypatch):
+    from tkinter import messagebox
+
+    _set_writable(read_only_window.repository.root, True)
+    asked = []
+    monkeypatch.setattr(
+        messagebox, "askyesno", lambda *args, **kwargs: asked.append(args) or False
+    )
+
+    read_only_window._recheck_store_access()
+    tk_root.update()
+
+    assert read_only_window.repository.read_only is False
+    assert "NUR LESEN" not in tk_root.title()
+    assert "NUR LESEN" not in read_only_window.store_var.get()
+    assert not read_only_window.messages.winfo_manager(), "der Warnbanner steht noch"
+    assert read_only_window.status_var.get() == "Der Store ist wieder beschreibbar."
+    assert asked, "der übersprungene Hausmeisterlauf wird nicht angeboten"
+
+
+def test_the_skipped_housekeeper_run_can_be_started_right_away(
+    read_only_window, tk_root, monkeypatch
+):
+    from tkinter import messagebox
+
+    _set_writable(read_only_window.repository.root, True)
+    monkeypatch.setattr(messagebox, "askyesno", lambda *args, **kwargs: True)
+
+    read_only_window._recheck_store_access()
+    tk_root.update()
+
+    assert (read_only_window.repository.root / "housekeeper.json").is_file()
+    assert read_only_window.status_var.get().startswith("Hausmeisterlauf beendet")
+
+
+def test_a_store_that_is_still_read_only_keeps_its_markers(read_only_window, tk_root):
+    read_only_window._recheck_store_access()
+    tk_root.update()
+
+    assert "NUR LESEN" in tk_root.title()
+    assert "NUR LESEN" in read_only_window.store_var.get()
+    assert read_only_window.messages.winfo_manager()
+    assert read_only_window.status_var.get() == "Der Store ist weiterhin schreibgeschützt."

tests/test_member_data_mail.py

@@ -0,0 +1,297 @@
+from contextlib import contextmanager
+from email.parser import BytesParser
+from email.policy import default
+
+import pytest
+
+from ccma.domain.models import Member
+from ccma.services.member_data_mail import (
+    data_review_recipients,
+    generate_data_review_mails,
+    mask_iban,
+    member_data_fields,
+    payment_reference,
+)
+from ccma.storage.repository import MemberRepository, RepositoryError
+
+
+def _store(tmp_path):
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+    organization = repository.get_configuration()["organization"]
+    organization.update(
+        {
+            "name": "Chaos Computer Club Mannheim e.V.",
+            "email": "verwaltung@example.org",
+            "iban": "DE98670505050038907751",
+            "bic": "MANSDE66XXX",
+        }
+    )
+    repository.save_organization(organization)
+    return repository
+
+
+def _member(repository, first_name, last_name, **values):
+    member = repository.create_member(
+        first_name=first_name, last_name=last_name, birth_date="1990-01-01"
+    )
+    for key, value in values.items():
+        setattr(member, key, value)
+    repository.save_member(member)
+    return repository.get_member(member.member_id)
+
+
+def test_the_mail_lists_the_stored_record_of_that_member(tmp_path):
+    repository = _store(tmp_path)
+    member = _member(
+        repository,
+        "Ada",
+        "Lovelace",
+        email="ada@example.org",
+        phone="0621 123456",
+        street="Hauptstraße 1",
+        postal_code="68159",
+        city="Mannheim",
+        status="active",
+        membership_started_at="2026-01-01",
+    )
+
+    generated, warnings = generate_data_review_mails(
+        repository,
+        [member.member_id],
+        delivery_mode="local",
+        output_directory=tmp_path / "out",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    assert warnings == []
+    message = BytesParser(policy=default).parsebytes(generated[0].export_path.read_bytes())
+    content = message.get_content()
+    assert message["To"] == "ada@example.org"
+    assert "Liebes Mitglied," in content
+    assert "folgende Daten haben wir über dich gespeichert" in content
+    assert "Name: Ada Lovelace" in content
+    assert "E-Mail: ada@example.org" in content
+    assert "Telefon: 0621 123456" in content
+    assert "PLZ und Ort: 68159 Mannheim" in content
+    assert "Mitglied seit: 01.01.2026" in content
+    assert "Zahlweise: Halbjährlich" in content
+    # Both halves identify a transfer on their own, so both are offered.
+    assert "deine Mitgliedsnummer und/oder deinen vollen Namen" in content
+    assert f"{member.member_number} – Ada Lovelace" in content
+    # Nothing bank-related is stored, so the note about the shortened IBAN is left
+    # out instead of pointing at a line that is not there.
+    assert "verkürzt" not in content
+    assert content.rstrip().endswith("Der Vorstand")
+
+
+def test_a_field_without_a_value_is_shown_as_missing_not_as_a_gap(tmp_path):
+    repository = _store(tmp_path)
+    member = _member(repository, "Ada", "Lovelace", email="ada@example.org")
+
+    fields = dict(member_data_fields(member))
+
+    assert fields["Telefon"] == "(nicht hinterlegt)"
+    assert fields["Mitglied seit"] == "(nicht hinterlegt)"
+    # Nothing bank-related is stored, so the member is not asked to check a mandate
+    # they never gave.
+    assert "IBAN" not in fields
+    assert "Mandatsreferenz" not in fields
+
+
+def test_bank_details_are_listed_with_a_masked_iban(tmp_path):
+    repository = _store(tmp_path)
+    member = _member(
+        repository,
+        "Ada",
+        "Lovelace",
+        email="ada@example.org",
+        account_holder="Ada Lovelace",
+        iban="DE98670505050038907751",
+        mandate_reference="MANDAT-42",
+        mandate_signed_at="2026-02-01",
+        mandate_active=True,
+    )
+
+    generated, _warnings = generate_data_review_mails(
+        repository,
+        [member.member_id],
+        delivery_mode="local",
+        output_directory=tmp_path / "out",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    content = BytesParser(policy=default).parsebytes(
+        generated[0].export_path.read_bytes()
+    ).get_content()
+    assert "IBAN: DE****************7751" in content
+    assert "DE98670505050038907751" not in content
+    assert "Mandatsreferenz: MANDAT-42" in content
+    assert "Lastschriftmandat: aktiv, erteilt am 01.02.2026" in content
+    assert "(Die IBAN zeigen wir absichtlich nur verkürzt an" in content
+
+
+def test_the_transfer_reference_joins_number_and_name():
+    member = Member(
+        member_id="1", member_number="CCMA-0007", first_name="Ada", last_name="Lovelace"
+    )
+
+    assert payment_reference(member) == "CCMA-0007 – Ada Lovelace"
+    # The store insists on a member number, but a record read from elsewhere may not
+    # have one -- the name then carries the reference without a dangling dash.
+    assert (
+        payment_reference(
+            Member(member_id="1", member_number="", first_name="Ada", last_name="Lovelace")
+        )
+        == "Ada Lovelace"
+    )
+
+
+def test_mask_iban_keeps_country_and_last_four_digits():
+    assert mask_iban("DE98 6705 0505 0038 9077 51") == "DE****************7751"
+    # Too short to mask meaningfully -- a broken value is shown as it is stored, so
+    # the member can tell the board it is wrong.
+    assert mask_iban("DE98") == "DE98"
+
+
+def test_every_selected_member_gets_their_own_mail_and_archive_copy(tmp_path):
+    repository = _store(tmp_path)
+    ada = _member(repository, "Ada", "Lovelace", email="ada@example.org", status="active")
+    grace = _member(repository, "Grace", "Hopper", email="grace@example.org", status="active")
+
+    generated, warnings = generate_data_review_mails(
+        repository,
+        [ada.member_id, grace.member_id],
+        delivery_mode="local",
+        output_directory=tmp_path / "out",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    assert warnings == []
+    assert [item.recipient for item in generated] == ["ada@example.org", "grace@example.org"]
+    for item in generated:
+        assert item.archive_path.parent.name == "Datenpruefung"
+        assert item.archive_path.read_bytes() == item.export_path.read_bytes()
+    ada_content = BytesParser(policy=default).parsebytes(
+        generated[0].archive_path.read_bytes()
+    ).get_content()
+    assert "Ada Lovelace" in ada_content
+    assert "Grace Hopper" not in ada_content
+    event = repository.get_events(grace.member_id)[-1]
+    assert event.event_type == "data_review_email_sent"
+    assert event.data["recipient"] == "grace@example.org"
+    assert event.references["document"].endswith(".eml")
+
+
+def test_a_member_without_an_address_is_reported_and_the_run_continues(tmp_path):
+    repository = _store(tmp_path)
+    silent = _member(repository, "Anon", "Ymous", status="active")
+    ada = _member(repository, "Ada", "Lovelace", email="ada@example.org", status="active")
+
+    generated, warnings = generate_data_review_mails(
+        repository,
+        [silent.member_id, ada.member_id],
+        delivery_mode="local",
+        output_directory=tmp_path / "out",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    assert [item.member_id for item in generated] == [ada.member_id]
+    assert warnings == [f"{silent.member_number}: E-Mail-Adresse fehlt."]
+    assert repository.get_events(silent.member_id)[-1].event_type != "data_review_email_sent"
+
+
+def test_default_recipients_are_the_live_memberships_with_an_address(tmp_path):
+    repository = _store(tmp_path)
+    _member(repository, "Ada", "Lovelace", email="ada@example.org", status="active")
+    _member(repository, "Grace", "Hopper", email="grace@example.org", status="honorary")
+    _member(repository, "Alan", "Turing", email="alan@example.org", status="ended")
+    _member(repository, "Anon", "Ymous", status="active")
+
+    names = [member.display_name for member in data_review_recipients(repository)]
+
+    assert names == ["Grace Hopper", "Ada Lovelace"]
+
+
+def test_send_mode_delivers_via_smtp_without_local_files(tmp_path, monkeypatch):
+    import ccma.services.member_data_mail as module
+
+    repository = _store(tmp_path)
+    member = _member(repository, "Ada", "Lovelace", email="ada@example.org", status="active")
+    repository.save_email_settings(
+        delivery_mode="send",
+        smtp_host="smtp.example.org",
+        smtp_port=587,
+        smtp_security="starttls",
+        smtp_username="verwaltung",
+        smtp_password="secret",
+        imap_host="",
+        imap_port=993,
+        imap_security="ssl",
+        imap_username="",
+        imap_password="",
+        imap_drafts_folder="INBOX.Entwürfe",
+    )
+    sent = []
+    monkeypatch.setattr(module, "smtp_session", contextmanager(lambda settings: iter(["client"])))
+    monkeypatch.setattr(module, "send_via_smtp", lambda client, content: sent.append(content))
+
+    generated, warnings = generate_data_review_mails(
+        repository,
+        [member.member_id],
+        delivery_mode="send",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    assert warnings == []
+    assert generated[0].export_path is None
+    assert generated[0].archive_path.read_bytes() == sent[0]
+    assert repository.get_events(member.member_id)[-1].data["delivery_mode"] == "send"
+
+
+def test_a_template_broken_outside_ccma_stops_that_member_without_archiving(tmp_path):
+    repository = _store(tmp_path)
+    member = _member(repository, "Ada", "Lovelace", email="ada@example.org", status="active")
+    (repository.mail_templates_root / "datenpruefung.txt").write_text(
+        "Betreff: Datenprüfung\n\nHallo,\n{{#data}}\n{{field.label}}\n", encoding="utf-8"
+    )
+
+    generated, warnings = generate_data_review_mails(
+        repository,
+        [member.member_id],
+        delivery_mode="local",
+        output_directory=tmp_path / "out",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    assert generated == []
+    assert "wird nicht geschlossen" in warnings[0]
+    archive = repository.members_root / member.member_id / "files" / "documents" / "Datenpruefung"
+    assert not any(archive.glob("*.eml"))
+    assert repository.get_events(member.member_id)[-1].event_type != "data_review_email_sent"
+
+
+def test_an_unknown_delivery_mode_is_refused(tmp_path):
+    repository = _store(tmp_path)
+
+    with pytest.raises(RepositoryError, match="Versandmodus"):
+        generate_data_review_mails(
+            repository,
+            [],
+            delivery_mode="postal",
+            sender_name="Verwaltung C3MA",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )

tests/test_options_dialog_ui.py

@@ -0,0 +1,161 @@
+from email.parser import BytesParser
+from email.policy import default
+
+import pytest
+
+pytest.importorskip("tkinter")
+
+from ccma.config import AppConfig  # noqa: E402
+from ccma.domain.mail_templates import placeholder_entries  # noqa: E402
+from ccma.services.welcome_mail import generate_and_send_welcome_mail  # noqa: E402
+from ccma.storage.repository import MemberRepository, RepositoryError  # noqa: E402
+
+
+@pytest.fixture
+def repository(tmp_path):
+    repository = MemberRepository(tmp_path / "store")
+    repository.initialize()
+    organization = repository.get_configuration()["organization"]
+    organization.update(
+        {
+            "name": "Chaos Computer Club Mannheim e.V.",
+            "email": "verwaltung@example.org",
+            "iban": "DE98670505050038907751",
+            "bic": "MANSDE66XXX",
+        }
+    )
+    repository.save_organization(organization)
+    return repository
+
+
+def _open_options(tk_root, repository):
+    from ccma.ui.options_dialog import OptionsDialog
+
+    dialog = OptionsDialog(tk_root, AppConfig(store_path=str(repository.root)), repository)
+    tk_root.update()
+    return dialog
+
+
+def _block_row(dialog):
+    for row in dialog.mail_template_placeholders.get_children():
+        label = str(dialog.mail_template_placeholders.item(row, "values")[0])
+        if label.startswith("{{#claims}}"):
+            return row
+    raise AssertionError("Der Wiederholungsblock fehlt in der Platzhalterliste.")
+
+
+def test_double_click_on_a_block_is_wired_up(tk_root, repository):
+    dialog = _open_options(tk_root, repository)
+    try:
+        assert dialog.mail_template_placeholders.bind("<Double-1>")
+        assert dialog.mail_template_snippets[_block_row(dialog)] == next(
+            entry.snippet
+            for entry in placeholder_entries("welcome")
+            if entry.label.startswith("{{#claims}}")
+        )
+    finally:
+        dialog.grab_release()
+        dialog.destroy()
+
+
+def test_inserting_a_block_puts_editable_template_code_into_the_body(tk_root, repository):
+    dialog = _open_options(tk_root, repository)
+    try:
+        dialog.mail_template_body.delete("1.0", "end")
+        dialog.mail_template_body.insert("1.0", "Offen sind aktuell:")
+        dialog.mail_template_placeholders.selection_set(_block_row(dialog))
+        dialog._insert_mail_placeholder()
+        tk_root.update()
+        body = dialog.mail_template_body.get("1.0", "end-1c")
+    finally:
+        dialog.grab_release()
+        dialog.destroy()
+
+    assert "…" not in body
+    assert "{{#claims}}" in body and "{{/claims}}" in body
+    assert "{{claim.description}}" in body
+    # The block was appended behind existing text and still starts on its own line.
+    assert body.splitlines()[0] == "Offen sind aktuell:"
+    assert body.splitlines()[1] == "{{#claims}}"
+
+
+def test_edited_template_survives_saving_and_produces_real_lines_in_the_mail(
+    tk_root, repository, tmp_path
+):
+    member = repository.create_member(
+        first_name="Ada", last_name="Lovelace", birth_date="1990-01-01"
+    )
+    member.email = "ada@example.org"
+    member.accepted_at = "2026-08-20"
+    repository.save_member(member)
+    repository.create_manual_claim(
+        member.member_id, title="Aufnahmegebühr", amount="15.00", due_date="2026-09-17"
+    )
+
+    dialog = _open_options(tk_root, repository)
+    try:
+        dialog.mail_template_subject_var.set("Willkommen, {{member.first_name}}")
+        dialog.mail_template_body.delete("1.0", "end")
+        dialog.mail_template_body.insert("1.0", "Offen sind aktuell:\n")
+        dialog.mail_template_placeholders.selection_set(_block_row(dialog))
+        dialog._insert_mail_placeholder()
+        tk_root.update()
+        dialog._save_mail_templates()
+    finally:
+        dialog.grab_release()
+        dialog.destroy()
+
+    generated = generate_and_send_welcome_mail(
+        repository,
+        member.member_id,
+        delivery_mode="local",
+        output_path=tmp_path / "Willkommen.eml",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    content = BytesParser(policy=default).parsebytes(
+        generated.export_path.read_bytes()
+    ).get_content()
+    assert "Aufnahmegebühr (fällig 17.09.2026): 15.00 Euro" in content
+    assert "…" not in content
+
+
+def test_the_dialog_refuses_to_save_an_unbalanced_block(tk_root, repository):
+    stored = repository.mail_templates_root / "willkommen.txt"
+    before = stored.read_text(encoding="utf-8")
+
+    dialog = _open_options(tk_root, repository)
+    try:
+        dialog.mail_template_body.delete("1.0", "end")
+        dialog.mail_template_body.insert("1.0", "Offen sind aktuell:\n{{#claims}}\n{{claim.title}}")
+        with pytest.raises(RepositoryError, match="wird nicht geschlossen"):
+            dialog._save_mail_templates()
+    finally:
+        dialog.grab_release()
+        dialog.destroy()
+
+    assert stored.read_text(encoding="utf-8") == before
+
+
+def test_a_broken_template_does_not_half_save_the_others(tk_root, repository):
+    reminder_file = repository.mail_templates_root / "mahnung.txt"
+    before = reminder_file.read_text(encoding="utf-8")
+
+    dialog = _open_options(tk_root, repository)
+    try:
+        # Edit a valid template first, then break the second one.
+        dialog.mail_template_var.set("Mahnung")
+        dialog._select_mail_template()
+        dialog.mail_template_body.insert("end", "\nP.S. Bitte Mitgliedsnummer angeben.")
+        dialog.mail_template_var.set("Willkommen & Erstrechnung")
+        dialog._select_mail_template()
+        dialog.mail_template_body.insert("end", "\n{{#claims}}\n{{claim.title}}")
+        with pytest.raises(RepositoryError, match="wird nicht geschlossen"):
+            dialog._save_mail_templates()
+    finally:
+        dialog.grab_release()
+        dialog.destroy()
+
+    assert reminder_file.read_text(encoding="utf-8") == before

tests/test_read_only_store.py

@@ -0,0 +1,253 @@
+import os
+import stat
+from datetime import date
+
+import pytest
+
+from ccma.domain.models import ContributionData
+from ccma.services.documents import DocumentService
+from ccma.services.housekeeper import Housekeeper
+from ccma.services.member_data_mail import generate_data_review_mails
+from ccma.services.reminder_mail import generate_and_send_reminder_mail
+from ccma.services.sepa_mail import generate_debit_mails
+from ccma.services.welcome_mail import generate_and_send_welcome_mail
+from ccma.storage.repository import MemberRepository, ReadOnlyStoreError
+
+# Root ignores the permission bits this test relies on, so the read-only mount it
+# stands in for cannot be simulated there.
+pytestmark = pytest.mark.skipif(
+    hasattr(os, "geteuid") and os.geteuid() == 0, reason="root bypasses file permissions"
+)
+
+
+def _set_writable(root, writable: bool) -> None:
+    mode_add = stat.S_IWUSR
+    for path in sorted(root.rglob("*"), reverse=True) + [root]:
+        current = stat.S_IMODE(path.stat().st_mode)
+        path.chmod(current | mode_add if writable else current & ~mode_add)
+
+
+@pytest.fixture
+def read_only_store(tmp_path):
+    root = tmp_path / "store"
+    repository = MemberRepository(root)
+    repository.initialize()
+    member = repository.create_member(
+        first_name="Ada", last_name="Lovelace", birth_date="1990-01-01"
+    )
+    # A complete member: without an address the mail services would bail out early
+    # for that reason, and the write they are actually being tested for is never
+    # reached.
+    member.email = "ada@example.org"
+    repository.save_member(member)
+    repository.save_contributions(
+        member.member_id,
+        ContributionData(
+            claims=[
+                {
+                    "claim_id": "claim-1",
+                    "claim_key": "overdue",
+                    "title": "Offene Forderung",
+                    "amount": "100.00",
+                    "due_date": "2026-01-31",
+                    "status": "open",
+                }
+            ]
+        ),
+    )
+    _set_writable(root, False)
+    yield MemberRepository(root), member
+    _set_writable(root, True)
+
+
+def test_a_writable_store_is_not_reported_as_read_only(tmp_path):
+    repository = MemberRepository(tmp_path / "store")
+    repository.initialize()
+
+    assert repository.read_only is False
+
+
+def test_store_directory_that_does_not_exist_yet_counts_as_writable(tmp_path):
+    assert MemberRepository(tmp_path / "not" / "created" / "yet").read_only is False
+
+
+def test_read_only_store_opens_and_stays_readable(read_only_store):
+    repository, member = read_only_store
+
+    assert repository.read_only is True
+    repository.initialize()
+    assert repository.validate() == []
+    assert [item.member_id for item in repository.list_members()] == [member.member_id]
+    assert repository.get_member(member.member_id).first_name == "Ada"
+    assert repository.get_contributions(member.member_id).claims
+    assert repository.get_events(member.member_id)
+    assert repository.get_configuration()["organization"]["name"]
+
+
+def test_every_write_is_refused_with_one_clear_message(read_only_store):
+    repository, member = read_only_store
+    stored = repository.get_member(member.member_id)
+
+    for action in (
+        lambda: repository.save_member(stored),
+        lambda: repository.create_member(first_name="Grace", last_name="Hopper"),
+        lambda: repository.create_manual_claim(
+            member.member_id, title="Beitrag", amount="10.00", due_date="2026-09-30"
+        ),
+        lambda: repository.save_contributions(member.member_id, ContributionData()),
+        lambda: repository.append_event(
+            member.member_id, event_type="comment", summary="Test", actor_type="user"
+        ),
+        lambda: repository.save_organization({"name": "Test", "iban": "", "bic": ""}),
+        lambda: repository.create_asset(label="Beamer"),
+    ):
+        with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+            action()
+
+
+def test_housekeeper_refuses_to_run_instead_of_failing_on_its_lock(read_only_store):
+    repository, _member = read_only_store
+
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        Housekeeper(repository).run(today=date(2026, 2, 10))
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        Housekeeper(repository).delete_task("some-key")
+    assert not (repository.root / ".housekeeper.lock").exists()
+
+
+def test_documents_and_mails_refuse_before_touching_the_member_file(read_only_store, tmp_path):
+    repository, member = read_only_store
+
+    service = DocumentService(repository)
+    template = next(item for item in service.list_templates() if item.name == "Mitglied")
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        service.generate(template, member.member_id, output_name="Test")
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        generate_and_send_reminder_mail(
+            repository,
+            member.member_id,
+            "claim-1",
+            "reminder-1",
+            delivery_mode="local",
+            output_path=tmp_path / "Mahnung.eml",
+            sender_name="Verwaltung",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        generate_and_send_welcome_mail(
+            repository,
+            member.member_id,
+            delivery_mode="local",
+            output_path=tmp_path / "Willkommen.eml",
+            sender_name="Verwaltung",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        generate_debit_mails(
+            repository,
+            [],
+            collection_date=date(2026, 9, 1),
+            delivery_mode="local",
+            output_directory=tmp_path / "sepa",
+            sender_name="Verwaltung",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        generate_data_review_mails(
+            repository,
+            [member.member_id],
+            delivery_mode="local",
+            output_directory=tmp_path / "datenpruefung",
+            sender_name="Verwaltung",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+
+
+def test_the_welcome_mail_writes_nothing_at_all_when_refused(read_only_store, tmp_path):
+    """The refusal has to come before rendering, sending and archiving -- not out of
+    the failing write at the end, by which point the mail would already be out."""
+    repository, member = read_only_store
+    export_path = tmp_path / "Willkommen.eml"
+
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        generate_and_send_welcome_mail(
+            repository,
+            member.member_id,
+            delivery_mode="local",
+            output_path=export_path,
+            sender_name="Verwaltung",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+
+    assert not export_path.exists()
+    files = repository.members_root / member.member_id / "files"
+    assert not (files / "documents" / "Willkommen").exists()
+    assert all(
+        event.event_type != "welcome_email_sent"
+        for event in repository.get_events(member.member_id)
+    )
+
+
+def test_uninitialized_read_only_store_reports_why_it_cannot_be_opened(tmp_path):
+    root = tmp_path / "empty-store"
+    root.mkdir()
+    root.chmod(stat.S_IRUSR | stat.S_IXUSR)
+    try:
+        with pytest.raises(ReadOnlyStoreError, match="repository.json"):
+            MemberRepository(root).initialize()
+    finally:
+        root.chmod(stat.S_IRWXU)
+
+
+def test_remounting_writable_is_picked_up_without_a_restart(read_only_store):
+    repository, _member = read_only_store
+    assert repository.read_only is True
+
+    _set_writable(repository.root, True)
+
+    assert repository.read_only is True, "the cached answer must stay put until refreshed"
+    assert repository.refresh_read_only() is False
+    repository.append_event(
+        _member.member_id,
+        event_type="comment",
+        summary="Wieder beschreibbar",
+        actor_type="user",
+    )
+
+
+def test_startup_sequence_completes_without_the_housekeeper(read_only_store):
+    """Mirrors what the splash screen's worker thread does -- this is the sequence
+    that used to abort the whole start with a PermissionError."""
+    repository, member = read_only_store
+
+    repository.initialize()
+    errors = repository.validate()
+    members = repository.list_members()
+    findings = [] if repository.read_only else Housekeeper(repository).run()
+
+    assert errors == []
+    assert [item.member_id for item in members] == [member.member_id]
+    assert findings == []
+    assert repository.member_count() == 1
+
+
+def test_mail_templates_fall_back_to_the_shipped_defaults(read_only_store):
+    """A store that predates mail templates has no templates/mail/ directory, and a
+    read-only one cannot get it -- the shipped default has to carry the session."""
+    from ccma.domain.mail_templates import default_mail_template
+
+    repository, _member = read_only_store
+    _set_writable(repository.root, True)
+    for path in repository.mail_templates_root.glob("*.txt"):
+        path.unlink()
+    _set_writable(repository.root, False)
+
+    assert repository.get_mail_template("welcome") == default_mail_template("welcome")
+    assert not list(repository.mail_templates_root.glob("*.txt")), "nothing was written"
+    with pytest.raises(ReadOnlyStoreError, match="schreibgeschützt"):
+        repository.save_mail_template("welcome", subject="Moin", body="Kurz.")

tests/test_reminder_mail.py

@@ -58,6 +58,59 @@ def test_reminder_mail_is_archived_and_marks_reminder_sent(tmp_path):
     assert generated.archive_path.parent.name == "Mahnungen"
 
 
+def test_a_dunning_mail_asks_for_a_transfer_even_with_an_active_mandate(tmp_path):
+    """A member is only dunned once the money did not arrive, so this claim has left
+    the direct-debit run -- "wir ziehen den Betrag ein, du musst nichts tun" would
+    contradict the very letter it accompanies."""
+    repository, member = _overdue_claim_repository(tmp_path / "store")
+    member.email = "reminder@example.org"
+    member.account_holder = "Reminder Test"
+    member.iban = "DE89370400440532013000"
+    member.mandate_reference = "MANDAT-1"
+    member.mandate_signed_at = "2026-01-01"
+    member.mandate_active = True
+    repository.save_member(member)
+    organization = repository.get_configuration()["organization"]
+    organization.update(
+        {
+            "name": "Chaos Computer Club Mannheim e.V.",
+            "email": "verwaltung@example.org",
+            "iban": "DE98670505050038907751",
+            "bic": "MANSDE66XXX",
+        }
+    )
+    repository.save_organization(organization)
+    # The shipped template spells the bank details out; this one uses the ready-made
+    # paragraph, which is what the placeholder chooser offers for a dunning mail.
+    repository.save_mail_template(
+        "reminder",
+        subject="Mahnung: {{claim.title}}",
+        body="Hallo {{member.first_name}},\n\n{{payment.instructions}}\n\n{{signature}}",
+    )
+    reminder = repository.create_reminder_draft(
+        member.member_id, "claim-1", level=1, name="Rücklastschrift", payment_deadline_days=14
+    )
+
+    generated = generate_and_send_reminder_mail(
+        repository,
+        member.member_id,
+        "claim-1",
+        reminder["reminder_id"],
+        delivery_mode="local",
+        output_path=tmp_path / "Mahnung.eml",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    content = BytesParser(policy=default).parsebytes(
+        generated.export_path.read_bytes()
+    ).get_content()
+    assert "Bitte überweise den Betrag" in content
+    assert "DE98670505050038907751" in content
+    assert "ziehen den Betrag" not in content
+
+
 def test_reminder_mail_includes_fee_in_open_balance(tmp_path):
     repository, member = _overdue_claim_repository(tmp_path / "store")
     member.email = "reminder@example.org"

tests/test_reminders.py

@@ -32,6 +32,15 @@ def _overdue_claim_repository(tmp_path):
     return repository, member
 
 
+def _sepa_member(repository, member):
+    member.iban = "DE89370400440532013000"
+    member.mandate_reference = "MANDATE-1"
+    member.mandate_signed_at = "2026-01-01"
+    member.mandate_active = True
+    repository.save_member(member)
+    return member
+
+
 def test_reminder_rule_progresses_only_after_sent_deadline(tmp_path) -> None:
     repository, member = _overdue_claim_repository(tmp_path)
     housekeeper = Housekeeper(repository)
@@ -136,11 +145,7 @@ def test_overdue_claim_and_reminder_finding_are_never_shown_at_once(tmp_path) ->
 
 def test_sepa_member_gets_debit_followup_instead_of_reminder(tmp_path) -> None:
     repository, member = _overdue_claim_repository(tmp_path)
-    member.iban = "DE89370400440532013000"
+    _sepa_member(repository, member)
-    member.mandate_reference = "MANDATE-1"
-    member.mandate_signed_at = "2026-01-01"
-    member.mandate_active = True
-    repository.save_member(member)
     housekeeper = Housekeeper(repository)
 
     findings = housekeeper.run(today=date(2026, 2, 10))
@@ -152,13 +157,12 @@ def test_sepa_member_gets_debit_followup_instead_of_reminder(tmp_path) -> None:
     assert "SEPA" in sepa_finding.detail
 
 
-def test_sepa_member_with_running_reminder_shows_awaiting_note_not_overdue(tmp_path) -> None:
+def test_a_dunned_sepa_claim_continues_in_the_normal_dunning_process(tmp_path) -> None:
+    """A bounced direct debit is dunned like any other claim: the money is expected as
+    a transfer from then on, so the "check the direct debit" notice must not come back
+    once the Rücklastschrift deadline has passed."""
     repository, member = _overdue_claim_repository(tmp_path)
-    member.iban = "DE89370400440532013000"
+    _sepa_member(repository, member)
-    member.mandate_reference = "MANDATE-1"
-    member.mandate_signed_at = "2026-01-01"
-    member.mandate_active = True
-    repository.save_member(member)
     housekeeper = Housekeeper(repository)
 
     draft = repository.create_reminder_draft(
@@ -177,20 +181,44 @@ def test_sepa_member_with_running_reminder_shows_awaiting_note_not_overdue(tmp_p
         for item in housekeeper.run(today=deadline - timedelta(days=1))
         if item.member_id == member.member_id
     ]
-
     assert not any(item.code == "sepa_debit_overdue" for item in findings)
-    awaiting = next(item for item in findings if item.code == "sepa_debit_awaiting_deadline")
+    awaiting = next(item for item in findings if item.code == "reminder_awaiting_deadline")
     assert awaiting.severity == "info"
     assert "Rücklastschrift" in awaiting.title
 
-    # Once the reminder's own deadline has passed without resolution, the plain SEPA
+    # Deadline gone by without payment: the next dunning level is due, not another
-    # follow-up notice returns so it doesn't just silently go quiet forever.
+    # "der Einzug muss geprüft werden".
     findings = [
-        item for item in housekeeper.run(today=deadline + timedelta(days=1))
+        item
+        for item in housekeeper.run(today=deadline + timedelta(days=1))
         if item.member_id == member.member_id
     ]
-    assert any(item.code == "sepa_debit_overdue" for item in findings)
+    assert not any(item.code == "sepa_debit_overdue" for item in findings)
-    assert not any(item.code == "sepa_debit_awaiting_deadline" for item in findings)
+    reminder_task = next(item for item in findings if item.code == "reminder_due")
+    assert "Erste Mahnung" in reminder_task.title
+    assert "Mahnstufe 2" in reminder_task.detail
+
+
+def test_an_undunned_sepa_claim_still_asks_to_check_the_debit(tmp_path) -> None:
+    repository, member = _overdue_claim_repository(tmp_path)
+    _sepa_member(repository, member)
+    housekeeper = Housekeeper(repository)
+
+    findings = [
+        item for item in housekeeper.run(today=date(2026, 2, 10)) if item.member_id == member.member_id
+    ]
+
+    # A draft alone changes nothing -- only a reminder that actually went out takes the
+    # claim out of the direct-debit run.
+    repository.create_reminder_draft(
+        member.member_id, "claim-1", level=1, name="Rücklastschrift", payment_deadline_days=14
+    )
+    still_sepa = [
+        item for item in housekeeper.run(today=date(2026, 2, 10)) if item.member_id == member.member_id
+    ]
+
+    assert {item.code for item in findings} == {"sepa_debit_overdue"}
+    assert {item.code for item in still_sepa} == {"sepa_debit_overdue"}
 
 
 def test_draft_can_be_cancelled_but_sent_reminder_cannot(tmp_path) -> None:

tests/test_sepa.py

@@ -63,6 +63,48 @@ def test_pending_debits_select_due_open_balance(tmp_path):
     assert debits[0].claim_ids == ("due",)
 
 
+def test_a_dunned_claim_is_not_collected_again(tmp_path):
+    """The dunning letter asked the member to transfer the money -- pulling it by
+    direct debit anyway would contradict it (and can bounce a second time)."""
+    repository, member = _repository(tmp_path)
+    draft = repository.create_reminder_draft(
+        member.member_id,
+        "due",
+        level=1,
+        name="Rücklastschrift",
+        payment_deadline_days=14,
+        items=[{"description": "Rücklastschriftgebühr", "amount": "5.00"}],
+    )
+
+    # A draft alone is not a dunning: nothing has gone out yet.
+    debits, warnings = pending_direct_debits(repository, due_until=date(2026, 12, 31))
+    assert [debit.claim_ids for debit in debits] == [("due",)]
+    assert warnings == []
+
+    repository.mark_reminder_sent(member.member_id, "due", draft["reminder_id"])
+    debits, warnings = pending_direct_debits(repository, due_until=date(2026, 12, 31))
+
+    # Nothing else is due in the window, so the member drops out of the run entirely
+    # -- and says why instead of vanishing silently.
+    assert debits == []
+    assert warnings == ["C3-42: „Mitgliedsbeitrag 2026“ wurde bereits gemahnt – "
+                        "Zahlung per Überweisung erwartet, kein erneuter Einzug."]
+
+
+def test_a_dunned_claim_does_not_hold_back_the_members_other_claims(tmp_path):
+    repository, member = _repository(tmp_path)
+    draft = repository.create_reminder_draft(
+        member.member_id, "due", level=1, name="Rücklastschrift", payment_deadline_days=14
+    )
+    repository.mark_reminder_sent(member.member_id, "due", draft["reminder_id"])
+
+    debits, warnings = pending_direct_debits(repository, due_until=date(2027, 12, 31))
+
+    assert [debit.claim_ids for debit in debits] == [("future",)]
+    assert debits[0].amount == Decimal("150.00")
+    assert len(warnings) == 1
+
+
 def test_pending_debits_follow_members_monthly_payment_frequency(tmp_path):
     repository, member = _repository(tmp_path)
     member.accepted_at = "2025-01-01"
@@ -178,11 +220,11 @@ def test_debit_mail_is_thunderbird_draft(tmp_path):
     debit = pending_direct_debits(repository, due_until=date(2026, 12, 31))[0][0]
 
     content = debit_mail_bytes(
-        recipient=member.email,
+        repository,
-        first_name=member.first_name,
+        member=member,
         debit=debit,
         collection_date=date(2026, 8, 3),
-        creditor_id="DE98ZZZ09999999999",
+        organization={"name": "C3MA", "creditor_id": "DE98ZZZ09999999999"},
         sender_name="Verwaltung C3MA",
         sender_email="verwaltung@example.org",
         signature="Der Vorstand",

tests/test_ui_imports.py

@@ -2,6 +2,7 @@ def test_ui_modules_import_without_creating_root_window() -> None:
     import ccma.app  # noqa: F401
     import ccma.ui.asset_tab  # noqa: F401
     import ccma.ui.claim_tab  # noqa: F401
+    import ccma.ui.data_review_mail_dialog  # noqa: F401
     import ccma.ui.main_window  # noqa: F401
     import ccma.ui.member_tab  # noqa: F401
     import ccma.ui.splash  # noqa: F401

tests/test_welcome_mail.py

@@ -0,0 +1,295 @@
+from contextlib import contextmanager
+from email.parser import BytesParser
+from email.policy import default
+
+import pytest
+
+from ccma.services.welcome_mail import generate_and_send_welcome_mail, open_claims
+from ccma.storage.repository import MemberRepository, RepositoryError
+
+
+def _new_member_repository(tmp_path):
+    repository = MemberRepository(tmp_path)
+    repository.initialize()
+    organization = repository.get_configuration()["organization"]
+    organization.update(
+        {
+            "name": "Chaos Computer Club Mannheim e.V.",
+            "email": "verwaltung@example.org",
+            "iban": "DE98670505050038907751",
+            "bic": "MANSDE66XXX",
+        }
+    )
+    repository.save_organization(organization)
+    member = repository.create_member(
+        first_name="Ada", last_name="Lovelace", birth_date="1990-01-01"
+    )
+    member.email = "ada@example.org"
+    member.accepted_at = "2026-08-20"
+    repository.save_member(member)
+    repository.create_manual_claim(
+        member.member_id, title="Aufnahmegebühr", amount="15.00", due_date="2026-09-17"
+    )
+    repository.create_manual_claim(
+        member.member_id,
+        title="Mitgliedsbeitrag 2. Halbjahr 2026",
+        amount="60.00",
+        due_date="2026-09-17",
+    )
+    return repository, member
+
+
+def test_welcome_mail_lists_open_claims_and_bank_details(tmp_path):
+    repository, member = _new_member_repository(tmp_path)
+    export_path = tmp_path / "Willkommen.eml"
+
+    generated = generate_and_send_welcome_mail(
+        repository,
+        member.member_id,
+        delivery_mode="local",
+        output_path=export_path,
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    message = BytesParser(policy=default).parsebytes(generated.export_path.read_bytes())
+    content = message.get_content()
+    assert message["To"] == "ada@example.org"
+    assert "Willkommen" in message["Subject"]
+    assert "Aufnahmegebühr (fällig 17.09.2026): 15.00 Euro" in content
+    assert "Mitgliedsbeitrag 2. Halbjahr 2026 (fällig 17.09.2026): 60.00 Euro" in content
+    assert "Gesamtbetrag: 75.00 Euro" in content
+    assert "DE98670505050038907751" in content
+    assert content.rstrip().endswith("Der Vorstand")
+    # No "Mitglied seit" is stored yet -- a member accepted in August starts on 1 September.
+    assert "Ab dem 01.09.2026 bist du offiziell Mitglied" in content
+
+
+def test_welcome_mail_is_archived_and_logged(tmp_path):
+    repository, member = _new_member_repository(tmp_path)
+
+    generated = generate_and_send_welcome_mail(
+        repository,
+        member.member_id,
+        delivery_mode="local",
+        output_path=tmp_path / "Willkommen.eml",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    assert generated.archive_path.parent.name == "Willkommen"
+    assert generated.archive_path.read_bytes() == generated.export_path.read_bytes()
+    event = repository.get_events(member.member_id)[-1]
+    assert event.event_type == "welcome_email_sent"
+    assert event.data["recipient"] == "ada@example.org"
+    assert len(event.data["claim_ids"]) == 2
+
+
+def test_only_selected_claims_are_billed(tmp_path):
+    repository, member = _new_member_repository(tmp_path)
+    admission = next(
+        claim for claim in open_claims(repository, member.member_id)
+        if claim["title"] == "Aufnahmegebühr"
+    )
+
+    generated = generate_and_send_welcome_mail(
+        repository,
+        member.member_id,
+        claim_ids=[admission["claim_id"]],
+        delivery_mode="local",
+        output_path=tmp_path / "Willkommen.eml",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    content = BytesParser(policy=default).parsebytes(
+        generated.export_path.read_bytes()
+    ).get_content()
+    assert "Aufnahmegebühr" in content
+    assert "Mitgliedsbeitrag 2. Halbjahr 2026" not in content
+    assert "Gesamtbetrag: 15.00 Euro" in content
+
+
+def test_members_with_mandate_are_told_the_money_is_collected(tmp_path):
+    repository, member = _new_member_repository(tmp_path)
+    member.account_holder = "Ada Lovelace"
+    member.iban = "DE98670505050038907751"
+    member.mandate_reference = "MANDAT-42"
+    member.mandate_signed_at = "2026-08-20"
+    member.mandate_active = True
+    repository.save_member(member)
+
+    generated = generate_and_send_welcome_mail(
+        repository,
+        member.member_id,
+        delivery_mode="local",
+        output_path=tmp_path / "Willkommen.eml",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    content = BytesParser(policy=default).parsebytes(
+        generated.export_path.read_bytes()
+    ).get_content()
+    assert "SEPA-Lastschriftmandat erteilt (Mandatsreferenz MANDAT-42)" in content
+    assert "Bitte überweise" not in content
+
+
+def test_edited_template_is_used_for_the_mail(tmp_path):
+    repository, member = _new_member_repository(tmp_path)
+    repository.save_mail_template(
+        "welcome",
+        subject="Servus {{member.first_name}}",
+        body="Du schuldest uns {{claims.total}} Euro.\n{{#claims}}* {{claim.title}}{{/claims}}",
+    )
+
+    generated = generate_and_send_welcome_mail(
+        repository,
+        member.member_id,
+        delivery_mode="local",
+        output_path=tmp_path / "Willkommen.eml",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    message = BytesParser(policy=default).parsebytes(generated.export_path.read_bytes())
+    assert message["Subject"] == "Servus Ada"
+    assert message.get_content().replace("\r\n", "\n").strip() == (
+        "Du schuldest uns 75.00 Euro.\n* Aufnahmegebühr\n* Mitgliedsbeitrag 2. Halbjahr 2026"
+    )
+
+
+def test_send_mode_delivers_via_smtp_without_local_file(tmp_path, monkeypatch):
+    import ccma.services.welcome_mail as welcome_mail_module
+
+    repository, member = _new_member_repository(tmp_path)
+    repository.save_email_settings(
+        delivery_mode="send",
+        smtp_host="smtp.example.org",
+        smtp_port=587,
+        smtp_security="starttls",
+        smtp_username="verwaltung",
+        smtp_password="secret",
+        imap_host="",
+        imap_port=993,
+        imap_security="ssl",
+        imap_username="",
+        imap_password="",
+        imap_drafts_folder="INBOX.Entwürfe",
+    )
+    sent = []
+    monkeypatch.setattr(
+        welcome_mail_module, "smtp_session", contextmanager(lambda settings: iter(["client"]))
+    )
+    monkeypatch.setattr(
+        welcome_mail_module, "send_via_smtp", lambda client, content: sent.append(content)
+    )
+
+    generated = generate_and_send_welcome_mail(
+        repository,
+        member.member_id,
+        delivery_mode="send",
+        sender_name="Verwaltung C3MA",
+        sender_email="verwaltung@example.org",
+        signature="Der Vorstand",
+    )
+
+    assert generated.export_path is None
+    assert generated.archive_path.read_bytes() == sent[0]
+    assert repository.get_events(member.member_id)[-1].data["delivery_mode"] == "send"
+
+
+def test_member_without_email_is_refused(tmp_path):
+    repository, member = _new_member_repository(tmp_path)
+    member.email = ""
+    repository.save_member(member)
+
+    with pytest.raises(RepositoryError, match="E-Mail-Adresse"):
+        generate_and_send_welcome_mail(
+            repository,
+            member.member_id,
+            delivery_mode="local",
+            output_path=tmp_path / "Willkommen.eml",
+            sender_name="Verwaltung C3MA",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+
+
+def test_archiving_failure_after_smtp_success_still_logs_the_sent_mail(tmp_path, monkeypatch):
+    import ccma.services.welcome_mail as welcome_mail_module
+
+    repository, member = _new_member_repository(tmp_path)
+    repository.save_email_settings(
+        delivery_mode="send",
+        smtp_host="mail.example.org",
+        smtp_port=587,
+        smtp_security="none",
+        smtp_username="",
+        smtp_password="",
+        imap_host="",
+        imap_port=993,
+        imap_security="ssl",
+        imap_username="",
+        imap_password="",
+        imap_drafts_folder="",
+    )
+    monkeypatch.setattr(
+        welcome_mail_module, "smtp_session", contextmanager(lambda settings: iter(["client"]))
+    )
+    monkeypatch.setattr(welcome_mail_module, "send_via_smtp", lambda client, content: None)
+    real_replace = welcome_mail_module.os.replace
+
+    def _flaky_replace(src, dst):
+        # Only the final move into the member file fails -- the mail is out by then.
+        if str(dst).endswith(".eml") and "Willkommen" in str(dst):
+            raise OSError("disk full")
+        return real_replace(src, dst)
+
+    monkeypatch.setattr(welcome_mail_module.os, "replace", _flaky_replace)
+
+    with pytest.raises(RepositoryError, match="zugestellt"):
+        generate_and_send_welcome_mail(
+            repository,
+            member.member_id,
+            delivery_mode="send",
+            sender_name="Verwaltung C3MA",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+
+    event = repository.get_events(member.member_id)[-1]
+    assert event.event_type == "welcome_email_sent"
+    assert event.data["archive_error"]
+    assert "document" not in event.references
+
+
+def test_a_template_broken_outside_ccma_stops_the_send(tmp_path):
+    repository, member = _new_member_repository(tmp_path)
+    # The templates are plain files in the store, so they can be edited (and broken)
+    # with any text editor -- the send has to notice instead of mailing the marker.
+    (repository.mail_templates_root / "willkommen.txt").write_text(
+        "Betreff: Willkommen\n\nHallo,\n{{#claims}}\n{{claim.title}}\n",
+        encoding="utf-8",
+    )
+
+    with pytest.raises(RepositoryError, match="wird nicht geschlossen"):
+        generate_and_send_welcome_mail(
+            repository,
+            member.member_id,
+            delivery_mode="local",
+            output_path=tmp_path / "Willkommen.eml",
+            sender_name="Verwaltung C3MA",
+            sender_email="verwaltung@example.org",
+            signature="Der Vorstand",
+        )
+
+    assert not (tmp_path / "Willkommen.eml").exists()
+    archive = repository.members_root / member.member_id / "files" / "documents" / "Willkommen"
+    assert not archive.exists()
+    assert repository.get_events(member.member_id)[-1].event_type != "welcome_email_sent"