diff --git a/.env.example b/.env.example
index a57adc7..21796b1 100644
--- a/.env.example
+++ b/.env.example
@@ -40,6 +40,16 @@ OIDC_CLIENT_SECRET=
 # redirect address registered at the provider is this plus /auth/callback.
 PUBLIC_BASE_URL=https://portal.example.test
 
+# Required. The mail server and mailbox the portal sends e-mail through, always over TLS.
+# SMTP_SECURITY is starttls (default, port 587) or ssl (port 465); SMTP_PORT overrides the port.
+# MAIL_FROM is the sender address, optionally with a display name: Portal <portal@example.test>
+SMTP_HOST=
+# SMTP_PORT=587
+# SMTP_SECURITY=starttls
+SMTP_USERNAME=
+SMTP_PASSWORD=
+MAIL_FROM=
+
 # Optional. Directory for the database. Default /data (the container volume).
 # DATA_DIR=/data
 
diff --git a/Dockerfile b/Dockerfile
index 1ee8413..9204a39 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -27,6 +27,7 @@ RUN SECRET_KEY=build-time-only-value-not-used-at-runtime-000000 \
     LDAP_CA_FILE=/app/README.md LDAP_PUBLISHER_GROUP_DN=build LDAP_ADMIN_GROUP_DN=build \
     OIDC_ISSUER=https://build.invalid/ OIDC_CLIENT_ID=build OIDC_CLIENT_SECRET=build \
     PUBLIC_BASE_URL=https://build.invalid \
+    SMTP_HOST=build.invalid SMTP_USERNAME=build SMTP_PASSWORD=build MAIL_FROM=build@build.invalid \
     sh -c '/app/.venv/bin/python manage.py compilemessages && /app/.venv/bin/python manage.py collectstatic --noinput'
 
 # Not part of the runtime image: `docker compose --profile test run --rm live-test`
diff --git a/README.md b/README.md
index e321135..360f46c 100644
--- a/README.md
+++ b/README.md
@@ -17,6 +17,12 @@ All configuration comes from environment variables, validated at startup. If any
 | `OIDC_CLIENT_ID` | yes | | Client ID of the provider's application |
 | `OIDC_CLIENT_SECRET` | yes | | Client secret of the provider's application |
 | `PUBLIC_BASE_URL` | yes | | Address users reach the portal at, scheme and host only. The provider's redirect address must be this plus `/auth/callback` |
+| `SMTP_HOST` | yes | | Host name of the mail server (no port, no URL) |
+| `SMTP_SECURITY` | no | `starttls` | `starttls` (port 587) or `ssl` (port 465); mail is never sent unencrypted and the server certificate is verified |
+| `SMTP_PORT` | no | 587 or 465 | Overrides the port |
+| `SMTP_USERNAME` | yes | | Mailbox user name |
+| `SMTP_PASSWORD` | yes | | Mailbox password |
+| `MAIL_FROM` | yes | | Sender address of every e-mail, optionally with a display name |
 | `LOG_LEVEL` | no | `INFO` | `DEBUG`, `INFO`, `WARNING`, `ERROR`, `CRITICAL` |
 | `LDAP_SERVER` | yes | | Directory server host name (optionally `:port`); LDAPS on 636 is always used and the name must be in the server's certificate |
 | `LDAP_USER_OU_DN` | yes | | Distinguished name of the OU whose users the portal may read and change |
@@ -61,6 +67,18 @@ Text is German (formal and informal) and English. The English text is the messag
 
 Theme, language and form of address are stored per device in the cookies `pm_theme`, `pm_lang` and `pm_form`; nothing is stored on the server.
 
+### Scheduler and e-mail
+
+One scheduler thread runs inside the single gunicorn worker and ticks every 30 seconds (`docker/gunicorn.conf.py`). Each tick runs the jobs in `portal/scheduler/services.py`; every run is recorded in `JobRun`. Other code never talks to the mail server: it calls `portal.mailer.services.enqueue(template, recipient, context)` inside its own transaction, and the `mail.flush` job sends from the outbox with retries (1, 5, 15 and 60 minutes between attempts, 5 attempts), at most 20 mails a minute. A mail that was being sent when the process stopped is marked failed and is not sent again.
+
+Mail templates live in `portal/templates/mail/<name>/subject.txt` and `body.txt`. They are rendered when queued, in the portal-wide language (`MAIL_LANGUAGE`, German formal), and the text is removed from the database once the mail is sent.
+
+To check the SMTP settings, queue and send a test mail from the running container:
+
+```sh
+docker compose exec portal python manage.py send_test_mail someone@example.test
+```
+
 ### Directory adapter against the test OU
 
 `uv sync` builds `python-ldap`, which needs the OpenLDAP and SASL development libraries (the Docker image installs them). The automated tests use an in-memory fake and a stand-in for the `ldap` module, so they run anywhere.
diff --git a/_bmad-output/initiative-ping-mee-portal/epic-platform-and-sign-in/story-scheduler-and-mail-outbox-plan.md b/_bmad-output/initiative-ping-mee-portal/epic-platform-and-sign-in/story-scheduler-and-mail-outbox-plan.md
new file mode 100644
index 0000000..4d00fe7
--- /dev/null
+++ b/_bmad-output/initiative-ping-mee-portal/epic-platform-and-sign-in/story-scheduler-and-mail-outbox-plan.md
@@ -0,0 +1,36 @@
+---
+title: 'Scheduler and mail outbox'
+type: 'feature'
+ticket: '7'
+created: '2026-10-18'
+status: 'built'
+baseline_revision: '0dc079a'
+route: 'full'
+route_source: 'auto'
+risk: 'medium'
+review: 'quick'
+review_source: 'pinned'
+context:
+  - '{project-root}/_bmad-output/architecture/architecture-ping-mee-self-service-platform-2026-10-15/ARCHITECTURE-SPINE.md'
+---
+
+## Intent
+
+**Problem:** Later epics must send e-mail (password change notices, confirmation links, announcements) without blocking requests, losing mail on restart or exceeding the provider's limits, and need a place to run repeating jobs.
+
+**Approach:** `adapters/mail` is the only code that talks SMTP (TLS always, certificate verified), with an in-memory fake. `mailer` owns the outbox; other code calls `enqueue(template, recipient, context)` in its own transaction. `scheduler` owns `JobRun` and one 30-second tick that runs idempotent jobs, started in the gunicorn worker by `docker/gunicorn.conf.py` (AD-11, AD-12, AD-19).
+
+## Decisions (made by the build; the spine left them open)
+
+- Retries: 5 attempts, waits of 1, 5, 15 and 60 minutes. Rate limit: 20 mails a minute. Named constants until the settings registry exists; the IONOS limit is still unknown (spec open question).
+- Mails are rendered when queued, in German formal (`MAIL_LANGUAGE`), as plain text only. HTML parts wait for the sanitizer (AD-16).
+- The body is removed from the database once the mail is sent or has failed, because it may hold a one-time link.
+- Restart safety: a row is claimed (`queued` to `sending`) before sending. A row still `sending` after 10 minutes is marked failed with an unknown outcome and is not sent again: a lost notice is better than a duplicate.
+- A refused login is treated as temporary, so a corrected password works on the next retry. A dead server stops the run after three consecutive outages.
+- `manage.py send_test_mail <address>` queues and sends a test mail at once, for the done check.
+- Only the `mail.flush` job exists; later entries add theirs to `JOBS`.
+
+## Implementation Notes
+
+- `pytest` 319 passed, 6 skipped; `ruff check` clean.
+- Not verified: a real SMTP server and the scheduler thread inside the container (needs the Linux host).
diff --git a/docker/entrypoint.sh b/docker/entrypoint.sh
index 2a37191..d333bce 100644
--- a/docker/entrypoint.sh
+++ b/docker/entrypoint.sh
@@ -4,6 +4,7 @@ set -eu
 python manage.py migrate --noinput
 
 exec gunicorn portal.config.wsgi:application \
+    --config /app/docker/gunicorn.conf.py \
     --bind 0.0.0.0:8000 \
     --workers 1 \
     --threads 4 \
diff --git a/docker/gunicorn.conf.py b/docker/gunicorn.conf.py
new file mode 100644
index 0000000..4ce1729
--- /dev/null
+++ b/docker/gunicorn.conf.py
@@ -0,0 +1,7 @@
+"""gunicorn settings that need code. The scheduler runs inside the single worker (AD-12)."""
+
+
+def post_worker_init(worker):
+    from portal.scheduler.runner import runner
+
+    runner.start()
diff --git a/portal/adapters/mail/__init__.py b/portal/adapters/mail/__init__.py
new file mode 100644
index 0000000..d871f73
--- /dev/null
+++ b/portal/adapters/mail/__init__.py
@@ -0,0 +1,15 @@
+"""Mail adapter: the only code that talks SMTP (AD-1)."""
+
+from .base import Mailer, MailError, MailMessage, MailRejected, MailUnavailable
+from .fake import FakeMailer
+from .smtp import SmtpMailer
+
+__all__ = [
+    "FakeMailer",
+    "MailError",
+    "MailMessage",
+    "MailRejected",
+    "MailUnavailable",
+    "Mailer",
+    "SmtpMailer",
+]
diff --git a/portal/adapters/mail/base.py b/portal/adapters/mail/base.py
new file mode 100644
index 0000000..a8c40f7
--- /dev/null
+++ b/portal/adapters/mail/base.py
@@ -0,0 +1,32 @@
+"""The mail interface the outbox uses (AD-1, AD-11)."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Protocol
+
+
+class MailError(Exception):
+    """Base class. Messages never contain the recipient or the text of the e-mail."""
+
+
+class MailUnavailable(MailError):
+    """The server could not take the message right now; trying again later may work."""
+
+
+class MailRejected(MailError):
+    """The server refused the message for good (for example an unknown recipient)."""
+
+
+@dataclass(frozen=True)
+class MailMessage:
+    sender: str
+    recipient: str
+    subject: str
+    body_text: str
+
+
+class Mailer(Protocol):
+    def send(self, message: MailMessage) -> None:
+        """Hand the message to the mail server, or raise MailUnavailable or MailRejected."""
+        ...
diff --git a/portal/adapters/mail/fake.py b/portal/adapters/mail/fake.py
new file mode 100644
index 0000000..5b96e3d
--- /dev/null
+++ b/portal/adapters/mail/fake.py
@@ -0,0 +1,24 @@
+"""In-memory mail server for tests (AD-1)."""
+
+from __future__ import annotations
+
+from .base import MailMessage, MailRejected, MailUnavailable
+
+
+class FakeMailer:
+    """Records what was sent. `unavailable` makes every send fail temporarily; recipients in
+    `rejected` are refused for good."""
+
+    def __init__(self) -> None:
+        self.sent: list[MailMessage] = []
+        self.unavailable = False
+        self.rejected: set[str] = set()
+        self.attempts = 0
+
+    def send(self, message: MailMessage) -> None:
+        self.attempts += 1
+        if self.unavailable:
+            raise MailUnavailable("The mail server is not available")
+        if message.recipient in self.rejected:
+            raise MailRejected("The mail server refused the message (550)")
+        self.sent.append(message)
diff --git a/portal/adapters/mail/smtp.py b/portal/adapters/mail/smtp.py
new file mode 100644
index 0000000..e72ad26
--- /dev/null
+++ b/portal/adapters/mail/smtp.py
@@ -0,0 +1,89 @@
+"""Sends e-mail through an SMTP server over TLS. The only module that talks SMTP (AD-1)."""
+
+from __future__ import annotations
+
+import logging
+import smtplib
+import ssl
+from email.message import EmailMessage
+from email.utils import formatdate, make_msgid
+
+from portal.config.env import SmtpConfig
+
+from .base import MailMessage, MailRejected, MailUnavailable
+
+logger = logging.getLogger(__name__)
+
+TIMEOUT_SECONDS = 20
+
+
+class SmtpMailer:
+    def __init__(self, config: SmtpConfig, smtp_module=smtplib) -> None:
+        self._config = config
+        self._smtp = smtp_module
+
+    def _build(self, message: MailMessage) -> EmailMessage:
+        email = EmailMessage()
+        # Setting a header that holds a line break raises ValueError, so no header injection.
+        email["From"] = message.sender
+        email["To"] = message.recipient
+        email["Subject"] = message.subject
+        email["Date"] = formatdate(localtime=False)
+        email["Message-ID"] = make_msgid(domain=self._config.host)
+        email.set_content(message.body_text, charset="utf-8")
+        return email
+
+    def _connect(self):
+        config = self._config
+        context = ssl.create_default_context()  # verifies the certificate and the host name
+        if config.security == "ssl":
+            connection = self._smtp.SMTP_SSL(
+                config.host, config.port, timeout=TIMEOUT_SECONDS, context=context
+            )
+        else:
+            connection = self._smtp.SMTP(config.host, config.port, timeout=TIMEOUT_SECONDS)
+        try:
+            connection.ehlo()
+            if config.security == "starttls":
+                connection.starttls(context=context)
+                connection.ehlo()
+            connection.login(config.username, config.password)
+        except BaseException:
+            connection.close()
+            raise
+        return connection
+
+    def send(self, message: MailMessage) -> None:
+        try:
+            email = self._build(message)
+        except ValueError as exc:
+            raise MailRejected("The message could not be built") from exc
+        try:
+            connection = self._connect()
+            try:
+                connection.send_message(email)
+            finally:
+                try:
+                    connection.quit()
+                except (self._smtp.SMTPException, OSError):
+                    connection.close()
+        except self._smtp.SMTPAuthenticationError as exc:
+            # A configuration problem: the Admin fixes it and the retry works.
+            logger.error("SMTP login refused (code %s)", exc.smtp_code)
+            raise MailUnavailable(f"The mail server refused the login ({exc.smtp_code})") from exc
+        except self._smtp.SMTPRecipientsRefused as exc:
+            codes = [code for code, _ in exc.recipients.values()]
+            raise _by_code(max(codes, default=0)) from exc
+        except self._smtp.SMTPResponseException as exc:
+            raise _by_code(exc.smtp_code) from exc
+        except (self._smtp.SMTPException, OSError, ssl.SSLError) as exc:
+            logger.warning("SMTP request failed: %s", type(exc).__name__)
+            name = type(exc).__name__
+            raise MailUnavailable(f"The mail server is not available ({name})") from exc
+
+
+def _by_code(code: int):
+    """Codes 5xx are permanent; everything else may work later."""
+    if 500 <= code < 600:
+        return MailRejected(f"The mail server refused the message ({code})")
+    return MailUnavailable(f"The mail server could not take the message ({code})")
diff --git a/portal/adapters/registry.py b/portal/adapters/registry.py
index 824c978..1ff2998 100644
--- a/portal/adapters/registry.py
+++ b/portal/adapters/registry.py
@@ -6,9 +6,11 @@ from django.conf import settings
 
 from .directory import Directory, LdapDirectory
 from .idp import Idp, OidcIdp
+from .mail import Mailer, SmtpMailer
 
 _directory: Directory | None = None
 _idp: Idp | None = None
+_mailer: Mailer | None = None
 
 
 def get_directory() -> Directory:
@@ -25,7 +27,16 @@ def get_idp() -> Idp:
     return _idp
 
 
-def install(directory: Directory | None = None, idp: Idp | None = None) -> None:
+def get_mailer() -> Mailer:
+    global _mailer
+    if _mailer is None:
+        _mailer = SmtpMailer(settings.SMTP)
+    return _mailer
+
+
+def install(
+    directory: Directory | None = None, idp: Idp | None = None, mailer: Mailer | None = None
+) -> None:
     """Replace the adapters (tests). Passing None for one leaves it to be built on first use."""
-    global _directory, _idp
-    _directory, _idp = directory, idp
+    global _directory, _idp, _mailer
+    _directory, _idp, _mailer = directory, idp, mailer
diff --git a/portal/config/env.py b/portal/config/env.py
index 77bb236..51b2293 100644
--- a/portal/config/env.py
+++ b/portal/config/env.py
@@ -5,10 +5,13 @@ from __future__ import annotations
 import ipaddress
 from collections.abc import Mapping
 from dataclasses import dataclass, field
+from email.utils import parseaddr
 from pathlib import Path
 from urllib.parse import urlsplit
 from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
+SMTP_SECURITY_MODES = ("starttls", "ssl")
+SMTP_DEFAULT_PORTS = {"starttls": 587, "ssl": 465}
 LOG_LEVELS = ("DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL")
 MIN_SECRET_KEY_LENGTH = 32
 _TRUE = {"1", "true", "yes", "on"}
@@ -55,6 +58,16 @@ class OidcConfig:
         return f"{self.public_base_url}/auth/callback"
 
 
+@dataclass(frozen=True)
+class SmtpConfig:
+    host: str
+    port: int
+    security: str  # "starttls" or "ssl"; mail is never sent unencrypted
+    username: str
+    password: str = field(repr=False)
+    sender: str  # the From address of every e-mail
+
+
 @dataclass(frozen=True)
 class Config:
     secret_key: str
@@ -66,6 +79,7 @@ class Config:
     default_timezone: str
     directory: DirectoryConfig
     oidc: OidcConfig
+    smtp: SmtpConfig
 
 
 def load_config(environ: Mapping[str, str]) -> Config:
@@ -162,6 +176,32 @@ def load_config(environ: Mapping[str, str]) -> Config:
         if parts.scheme not in allowed or not parts.netloc or parts.path or parts.query:
             problems.append("PUBLIC_BASE_URL: must be an https origin such as https://host")
 
+    smtp_host = required("SMTP_HOST", "host name of the mail server")
+    if "://" in smtp_host or "/" in smtp_host or ":" in smtp_host:
+        problems.append("SMTP_HOST: must be a host name only; set the port in SMTP_PORT")
+    smtp_security = (raw("SMTP_SECURITY") or "starttls").lower()
+    if smtp_security not in SMTP_SECURITY_MODES:
+        problems.append(f"SMTP_SECURITY: must be one of {', '.join(SMTP_SECURITY_MODES)}")
+        smtp_security = "starttls"
+    smtp_port = SMTP_DEFAULT_PORTS[smtp_security]
+    port_raw = raw("SMTP_PORT")
+    if port_raw is not None:
+        if port_raw.isdigit() and 0 < int(port_raw) < 65536:
+            smtp_port = int(port_raw)
+        else:
+            problems.append("SMTP_PORT: must be a port number from 1 to 65535")
+    smtp_username = required("SMTP_USERNAME", "user name of the mailbox")
+    smtp_password = required("SMTP_PASSWORD", "password of the mailbox")
+    sender = required("MAIL_FROM", "sender address of the portal's e-mails")
+    address = parseaddr(sender)[1]
+    if sender and (
+        address.count("@") != 1
+        or any(c in sender for c in chr(13) + chr(10))
+        or address.startswith("@")
+        or address.endswith("@")
+    ):
+        problems.append("MAIL_FROM: must be an e-mail address, optionally with a display name")
+
     if problems:
         raise ConfigError(problems)
 
@@ -188,4 +228,12 @@ def load_config(environ: Mapping[str, str]) -> Config:
             client_secret=client_secret,
             public_base_url=base_url,
         ),
+        smtp=SmtpConfig(
+            host=smtp_host,
+            port=smtp_port,
+            security=smtp_security,
+            username=smtp_username,
+            password=smtp_password,
+            sender=sender,
+        ),
     )
diff --git a/portal/config/settings.py b/portal/config/settings.py
index 502b0d3..2a71c90 100644
--- a/portal/config/settings.py
+++ b/portal/config/settings.py
@@ -25,6 +25,7 @@ DATA_DIR = _config.data_dir
 DISPLAY_TIME_ZONE = _config.default_timezone
 DIRECTORY = _config.directory
 OIDC = _config.oidc
+SMTP = _config.smtp
 
 INSTALLED_APPS = [
     "django.contrib.contenttypes",
@@ -34,6 +35,8 @@ INSTALLED_APPS = [
     "portal.audit",
     "portal.accounts",
     "portal.shell",
+    "portal.mailer",
+    "portal.scheduler",
 ]
 
 MIDDLEWARE = [
@@ -90,6 +93,10 @@ LANGUAGE_CODE = "en"
 LANGUAGES = [("en", "English"), ("de", "Deutsch")]
 LOCALE_PATHS = [BASE_DIR / "portal" / "locale"]
 
+# E-mails use the portal-wide language and form of address (a per-device choice cannot reach
+# server-sent mail). Becomes a runtime setting with the settings registry.
+MAIL_LANGUAGE = "de"
+
 # Static files served by whitenoise; assets are built into the image.
 STATIC_URL = "static/"
 STATIC_ROOT = BASE_DIR / "staticfiles"
diff --git a/portal/locale/de/LC_MESSAGES/django.po b/portal/locale/de/LC_MESSAGES/django.po
index cfa938f..48a6ab1 100644
--- a/portal/locale/de/LC_MESSAGES/django.po
+++ b/portal/locale/de/LC_MESSAGES/django.po
@@ -107,3 +107,9 @@ msgstr "Protokoll"
 
 msgid "Status"
 msgstr "Status"
+
+msgid "Test e-mail from the portal"
+msgstr "Test-E-Mail vom Portal"
+
+msgid "This is a test e-mail from the portal. If you can read it, sending e-mail works."
+msgstr "Das ist eine Test-E-Mail vom Portal. Wenn Sie sie lesen können, funktioniert der E-Mail-Versand."
diff --git a/portal/locale/de_DU/LC_MESSAGES/django.po b/portal/locale/de_DU/LC_MESSAGES/django.po
index d985de7..5b3d32d 100644
--- a/portal/locale/de_DU/LC_MESSAGES/django.po
+++ b/portal/locale/de_DU/LC_MESSAGES/django.po
@@ -26,3 +26,6 @@ msgstr "Du wurdest abgemeldet."
 
 msgid "This is not possible right now. Please try again later."
 msgstr "Das ist gerade nicht möglich. Bitte versuche es später erneut."
+
+msgid "This is a test e-mail from the portal. If you can read it, sending e-mail works."
+msgstr "Das ist eine Test-E-Mail vom Portal. Wenn du sie lesen kannst, funktioniert der E-Mail-Versand."
diff --git a/portal/mailer/__init__.py b/portal/mailer/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/portal/mailer/apps.py b/portal/mailer/apps.py
new file mode 100644
index 0000000..84014ba
--- /dev/null
+++ b/portal/mailer/apps.py
@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class MailerConfig(AppConfig):
+    name = "portal.mailer"
+    label = "mailer"
diff --git a/portal/mailer/management/__init__.py b/portal/mailer/management/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/portal/mailer/management/commands/__init__.py b/portal/mailer/management/commands/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/portal/mailer/management/commands/send_test_mail.py b/portal/mailer/management/commands/send_test_mail.py
new file mode 100644
index 0000000..b332b55
--- /dev/null
+++ b/portal/mailer/management/commands/send_test_mail.py
@@ -0,0 +1,28 @@
+from django.core.management.base import BaseCommand, CommandError
+
+from portal.mailer import services
+from portal.mailer.models import OutboxMail
+
+
+class Command(BaseCommand):
+    help = "Queue a test e-mail and send it now, to check the SMTP settings."
+
+    def add_arguments(self, parser):
+        parser.add_argument("recipient", help="E-mail address that should receive the test mail")
+
+    def handle(self, *args, recipient, **options):
+        try:
+            mail = services.enqueue("test", recipient)
+        except ValueError as exc:
+            raise CommandError(str(exc)) from exc
+        result = services.flush()
+        mail.refresh_from_db()
+        self.stdout.write(f"Outbox entry {mail.pk}: {mail.status} ({result})")
+        if mail.status == OutboxMail.Status.SENT:
+            self.stdout.write("The mail server accepted the message.")
+        elif mail.status == OutboxMail.Status.QUEUED:
+            self.stdout.write(f"Not sent yet, will be retried: {mail.last_error}")
+            raise SystemExit(1)
+        else:
+            self.stdout.write(f"Failed: {mail.last_error}")
+            raise SystemExit(1)
diff --git a/portal/mailer/migrations/0001_initial.py b/portal/mailer/migrations/0001_initial.py
new file mode 100644
index 0000000..8ee6966
--- /dev/null
+++ b/portal/mailer/migrations/0001_initial.py
@@ -0,0 +1,35 @@
+# Generated by Django 5.2.18 on 2026-10-18 07:16
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='OutboxMail',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('template', models.CharField(max_length=100)),
+                ('recipient', models.CharField(max_length=254)),
+                ('subject', models.CharField(max_length=300)),
+                ('body_text', models.TextField(blank=True)),
+                ('status', models.CharField(choices=[('queued', 'Queued'), ('sending', 'Sending'), ('sent', 'Sent'), ('failed', 'Failed')], default='queued', max_length=10)),
+                ('attempts', models.PositiveSmallIntegerField(default=0)),
+                ('created_at', models.DateTimeField()),
+                ('next_attempt_at', models.DateTimeField()),
+                ('claimed_at', models.DateTimeField(blank=True, null=True)),
+                ('sent_at', models.DateTimeField(blank=True, null=True)),
+                ('last_error', models.CharField(blank=True, max_length=200)),
+            ],
+            options={
+                'ordering': ['id'],
+                'indexes': [models.Index(fields=['status', 'next_attempt_at'], name='mailer_outb_status_d5af6e_idx')],
+            },
+        ),
+    ]
diff --git a/portal/mailer/migrations/__init__.py b/portal/mailer/migrations/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/portal/mailer/models.py b/portal/mailer/models.py
new file mode 100644
index 0000000..9cf6ecf
--- /dev/null
+++ b/portal/mailer/models.py
@@ -0,0 +1,29 @@
+from django.db import models
+
+
+class OutboxMail(models.Model):
+    """One e-mail waiting to be sent, being sent, sent or failed. Owned by `mailer` (AD-19)."""
+
+    class Status(models.TextChoices):
+        QUEUED = "queued"
+        SENDING = "sending"
+        SENT = "sent"
+        FAILED = "failed"
+
+    template = models.CharField(max_length=100)
+    recipient = models.CharField(max_length=254)
+    subject = models.CharField(max_length=300)
+    # Kept only until the mail is sent: it may hold a one-time link.
+    body_text = models.TextField(blank=True)
+    status = models.CharField(max_length=10, choices=Status.choices, default=Status.QUEUED)
+    attempts = models.PositiveSmallIntegerField(default=0)
+    created_at = models.DateTimeField()
+    next_attempt_at = models.DateTimeField()
+    claimed_at = models.DateTimeField(null=True, blank=True)
+    sent_at = models.DateTimeField(null=True, blank=True)
+    # What went wrong, in words without the recipient or the text of the mail.
+    last_error = models.CharField(max_length=200, blank=True)
+
+    class Meta:
+        indexes = [models.Index(fields=["status", "next_attempt_at"])]
+        ordering = ["id"]
diff --git a/portal/mailer/services.py b/portal/mailer/services.py
new file mode 100644
index 0000000..b490ede
--- /dev/null
+++ b/portal/mailer/services.py
@@ -0,0 +1,151 @@
+"""The outbox: other modules call `enqueue`, the scheduler calls `flush` (AD-11).
+
+A mail is claimed (queued -> sending) before it is handed to the server, so two runs never
+send the same row. If the process dies in between, the row stays `sending`; later it is marked
+failed with an unknown outcome and is not sent again, because a lost mail is better than a
+duplicate one for a password or sign-in notice.
+"""
+
+from __future__ import annotations
+
+import logging
+import re
+from dataclasses import dataclass
+from datetime import datetime, timedelta
+
+from django.conf import settings
+from django.db.models import F
+from django.template.loader import render_to_string
+from django.utils import timezone, translation
+
+from portal.adapters.mail import MailMessage, MailRejected, MailUnavailable
+from portal.adapters.registry import get_mailer
+
+from .models import OutboxMail
+
+logger = logging.getLogger(__name__)
+
+MAX_ATTEMPTS = 5
+BACKOFF_SECONDS = (60, 5 * 60, 15 * 60, 60 * 60)  # wait after the 1st, 2nd, ... failed attempt
+RATE_PER_MINUTE = 20
+LEASE_SECONDS = 10 * 60  # a row that has been `sending` this long is given up on
+STOP_AFTER_CONSECUTIVE_OUTAGES = 3
+
+_ADDRESS = re.compile(r"^[^@\s<>,;\"()\[\]\\]+@[^@\s<>,;\"()\[\]\\]+\.[^@\s<>,;\"()\[\]\\]+$")
+
+
+@dataclass(frozen=True)
+class FlushResult:
+    sent: int = 0
+    retried: int = 0
+    failed: int = 0
+
+    def __str__(self) -> str:
+        return f"sent={self.sent} retried={self.retried} failed={self.failed}"
+
+
+def is_valid_address(value: str) -> bool:
+    return len(value) <= 254 and bool(_ADDRESS.match(value))
+
+
+def enqueue(template: str, recipient: str, context: dict | None = None) -> OutboxMail:
+    """Render the e-mail in the portal-wide language and queue it.
+
+    Call it inside the transaction of the change that causes the mail, so a rolled-back change
+    queues nothing.
+    """
+    if not is_valid_address(recipient):
+        raise ValueError("Not a usable e-mail address")
+    with translation.override(settings.MAIL_LANGUAGE):
+        subject = render_to_string(f"mail/{template}/subject.txt", context or {})
+        body = render_to_string(f"mail/{template}/body.txt", context or {})
+    subject = " ".join(subject.split())  # one line, whatever the template did
+    now = timezone.now()
+    return OutboxMail.objects.create(
+        template=template,
+        recipient=recipient,
+        subject=subject[:300],
+        body_text=body.strip() + "\n",
+        created_at=now,
+        next_attempt_at=now,
+    )
+
+
+def _give_up_on_stale(now: datetime) -> None:
+    stale = OutboxMail.objects.filter(
+        status=OutboxMail.Status.SENDING, claimed_at__lt=now - timedelta(seconds=LEASE_SECONDS)
+    )
+    count = stale.update(
+        status=OutboxMail.Status.FAILED,
+        body_text="",
+        last_error="Outcome unknown after a restart; not sent again",
+    )
+    if count:
+        logger.error("Gave up on %s mails that were being sent when the process stopped", count)
+
+
+def _backoff(attempts: int) -> timedelta:
+    return timedelta(seconds=BACKOFF_SECONDS[min(attempts, len(BACKOFF_SECONDS)) - 1])
+
+
+def flush(now: datetime | None = None) -> FlushResult:
+    """Send what is due, within the rate limit. Safe to call repeatedly."""
+    now = now or timezone.now()
+    _give_up_on_stale(now)
+    recent = OutboxMail.objects.filter(
+        status=OutboxMail.Status.SENT, sent_at__gt=now - timedelta(minutes=1)
+    ).count()
+    budget = max(RATE_PER_MINUTE - recent, 0)
+    due = list(
+        OutboxMail.objects.filter(status=OutboxMail.Status.QUEUED, next_attempt_at__lte=now)
+        .order_by("id")
+        .values_list("pk", flat=True)[:budget]
+    )
+    sent = retried = failed = outages = 0
+    mailer = get_mailer()
+    for pk in due:
+        claimed = OutboxMail.objects.filter(pk=pk, status=OutboxMail.Status.QUEUED).update(
+            status=OutboxMail.Status.SENDING, claimed_at=now, attempts=F("attempts") + 1
+        )
+        if not claimed:  # another run took it
+            continue
+        mail = OutboxMail.objects.get(pk=pk)
+        message = MailMessage(
+            sender=settings.SMTP.sender,
+            recipient=mail.recipient,
+            subject=mail.subject,
+            body_text=mail.body_text,
+        )
+        try:
+            mailer.send(message)
+        except MailUnavailable as exc:
+            outages += 1
+            if mail.attempts >= MAX_ATTEMPTS:
+                _finish(mail, OutboxMail.Status.FAILED, str(exc))
+                failed += 1
+            else:
+                mail.status = OutboxMail.Status.QUEUED
+                mail.next_attempt_at = now + _backoff(mail.attempts)
+                mail.last_error = str(exc)[:200]
+                mail.save(update_fields=["status", "next_attempt_at", "last_error"])
+                retried += 1
+            logger.warning("Mail %s not sent (attempt %s)", pk, mail.attempts)
+            if outages >= STOP_AFTER_CONSECUTIVE_OUTAGES:
+                break
+        except MailRejected as exc:
+            _finish(mail, OutboxMail.Status.FAILED, str(exc))
+            failed += 1
+            logger.warning("Mail %s was refused", pk)
+        else:
+            outages = 0
+            _finish(mail, OutboxMail.Status.SENT, "", sent_at=now)
+            sent += 1
+    return FlushResult(sent, retried, failed)
+
+
+def _finish(mail: OutboxMail, status: str, error: str, sent_at: datetime | None = None) -> None:
+    mail.status = status
+    mail.last_error = error[:200]
+    mail.body_text = ""
+    mail.sent_at = sent_at
+    mail.save(update_fields=["status", "last_error", "body_text", "sent_at"])
diff --git a/portal/scheduler/__init__.py b/portal/scheduler/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/portal/scheduler/apps.py b/portal/scheduler/apps.py
new file mode 100644
index 0000000..80fd91c
--- /dev/null
+++ b/portal/scheduler/apps.py
@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class SchedulerConfig(AppConfig):
+    name = "portal.scheduler"
+    label = "scheduler"
diff --git a/portal/scheduler/migrations/0001_initial.py b/portal/scheduler/migrations/0001_initial.py
new file mode 100644
index 0000000..05a4d20
--- /dev/null
+++ b/portal/scheduler/migrations/0001_initial.py
@@ -0,0 +1,29 @@
+# Generated by Django 5.2.18 on 2026-10-18 07:16
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='JobRun',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('job', models.CharField(max_length=60)),
+                ('started_at', models.DateTimeField()),
+                ('finished_at', models.DateTimeField(blank=True, null=True)),
+                ('status', models.CharField(choices=[('running', 'Running'), ('ok', 'Ok'), ('error', 'Error')], default='running', max_length=10)),
+                ('detail', models.CharField(blank=True, max_length=200)),
+            ],
+            options={
+                'ordering': ['-started_at', '-id'],
+                'indexes': [models.Index(fields=['job', '-started_at'], name='scheduler_j_job_2c7e36_idx')],
+            },
+        ),
+    ]
diff --git a/portal/scheduler/migrations/__init__.py b/portal/scheduler/migrations/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/portal/scheduler/models.py b/portal/scheduler/models.py
new file mode 100644
index 0000000..dbc485f
--- /dev/null
+++ b/portal/scheduler/models.py
@@ -0,0 +1,21 @@
+from django.db import models
+
+
+class JobRun(models.Model):
+    """The record of one run of one job. Owned by `scheduler` (AD-19)."""
+
+    class Status(models.TextChoices):
+        RUNNING = "running"
+        OK = "ok"
+        ERROR = "error"
+
+    job = models.CharField(max_length=60)
+    started_at = models.DateTimeField()
+    finished_at = models.DateTimeField(null=True, blank=True)
+    status = models.CharField(max_length=10, choices=Status.choices, default=Status.RUNNING)
+    # A short summary, or the name of the error. Never personal content.
+    detail = models.CharField(max_length=200, blank=True)
+
+    class Meta:
+        indexes = [models.Index(fields=["job", "-started_at"])]
+        ordering = ["-started_at", "-id"]
diff --git a/portal/scheduler/runner.py b/portal/scheduler/runner.py
new file mode 100644
index 0000000..8105b16
--- /dev/null
+++ b/portal/scheduler/runner.py
@@ -0,0 +1,51 @@
+"""The scheduler thread: one per process, one tick every 30 seconds (AD-12)."""
+
+from __future__ import annotations
+
+import logging
+import threading
+from collections.abc import Callable
+
+from django.db import close_old_connections
+
+from . import services
+
+logger = logging.getLogger(__name__)
+
+TICK_SECONDS = 30
+
+
+class Runner:
+    def __init__(self, tick: Callable[[], None] = services.tick, interval: float = TICK_SECONDS):
+        self._tick = tick
+        self._interval = interval
+        self._stop = threading.Event()
+        self._thread: threading.Thread | None = None
+
+    def start(self) -> None:
+        """Start the thread; calling it again while it runs does nothing."""
+        if self._thread is not None and self._thread.is_alive():
+            return
+        self._stop.clear()
+        self._thread = threading.Thread(target=self._loop, name="scheduler", daemon=True)
+        self._thread.start()
+
+    def stop(self, timeout: float = 5) -> None:
+        self._stop.set()
+        if self._thread is not None:
+            self._thread.join(timeout)
+
+    def _loop(self) -> None:
+        logger.info("Scheduler started")
+        while not self._stop.is_set():
+            try:
+                self._tick()
+            except Exception:
+                logger.exception("Scheduler tick failed")
+            finally:
+                close_old_connections()
+            self._stop.wait(self._interval)
+        logger.info("Scheduler stopped")
+
+
+runner = Runner()
diff --git a/portal/scheduler/services.py b/portal/scheduler/services.py
new file mode 100644
index 0000000..f5c3304
--- /dev/null
+++ b/portal/scheduler/services.py
@@ -0,0 +1,48 @@
+"""Jobs and one tick that runs them (AD-12).
+
+Every job reads the database for what is due and is safe to repeat, so a missed or doubled
+tick does no harm. Each run is recorded for the Admin status page.
+"""
+
+from __future__ import annotations
+
+import logging
+from collections.abc import Callable
+from dataclasses import dataclass
+from datetime import datetime, timedelta
+
+from django.utils import timezone
+
+from portal.mailer import services as mailer
+
+from .models import JobRun
+
+logger = logging.getLogger(__name__)
+
+KEEP_RUNS_DAYS = 7
+
+
+@dataclass(frozen=True)
+class Job:
+    name: str
+    run: Callable[[datetime], object]  # returns something printable as the run's summary
+
+
+# The order is the order they run in. Later entries add jobs here.
+JOBS: tuple[Job, ...] = (Job("mail.flush", lambda now: mailer.flush(now)),)
+
+
+def tick(now: datetime | None = None, jobs: tuple[Job, ...] | None = None) -> None:
+    """Run every job once. A failing job is recorded and does not stop the others."""
+    now = now or timezone.now()
+    for job in JOBS if jobs is None else jobs:
+        run = JobRun.objects.create(job=job.name, started_at=now)
+        try:
+            detail = str(job.run(now))
+            status = JobRun.Status.OK
+        except Exception as exc:
+            logger.exception("Job %s failed", job.name)
+            detail, status = type(exc).__name__, JobRun.Status.ERROR
+        run.status, run.detail, run.finished_at = status, detail[:200], timezone.now()
+        run.save(update_fields=["status", "detail", "finished_at"])
+    JobRun.objects.filter(started_at__lt=now - timedelta(days=KEEP_RUNS_DAYS)).delete()
diff --git a/portal/templates/mail/test/body.txt b/portal/templates/mail/test/body.txt
new file mode 100644
index 0000000..df7d6f2
--- /dev/null
+++ b/portal/templates/mail/test/body.txt
@@ -0,0 +1 @@
+{% load i18n %}{% autoescape off %}{% trans "This is a test e-mail from the portal. If you can read it, sending e-mail works." %}{% endautoescape %}
diff --git a/portal/templates/mail/test/subject.txt b/portal/templates/mail/test/subject.txt
new file mode 100644
index 0000000..84b2cea
--- /dev/null
+++ b/portal/templates/mail/test/subject.txt
@@ -0,0 +1 @@
+{% load i18n %}{% autoescape off %}{% trans "Test e-mail from the portal" %}{% endautoescape %}
diff --git a/portal/tests/conftest.py b/portal/tests/conftest.py
index c3e8690..ebd4da3 100644
--- a/portal/tests/conftest.py
+++ b/portal/tests/conftest.py
@@ -7,6 +7,7 @@ import pytest
 from portal.adapters import registry
 from portal.adapters.directory import FakeDirectory
 from portal.adapters.idp import FakeIdp
+from portal.adapters.mail import FakeMailer
 
 
 @pytest.fixture
@@ -28,14 +29,18 @@ def valid_env(tmp_path):
         "OIDC_CLIENT_ID": "portal-client",
         "OIDC_CLIENT_SECRET": "client-secret",
         "PUBLIC_BASE_URL": "https://portal.example.test",
+        "SMTP_HOST": "mail.example.test",
+        "SMTP_USERNAME": "portal@example.test",
+        "SMTP_PASSWORD": "mail-password",
+        "MAIL_FROM": "Portal <portal@example.test>",
     }
 
 
 @pytest.fixture(autouse=True)
 def adapters():
     """Fakes for every adapter, so no test can reach a real directory or provider."""
-    fakes = SimpleNamespace(directory=FakeDirectory(), idp=FakeIdp())
-    registry.install(fakes.directory, fakes.idp)
+    fakes = SimpleNamespace(directory=FakeDirectory(), idp=FakeIdp(), mailer=FakeMailer())
+    registry.install(fakes.directory, fakes.idp, fakes.mailer)
     yield fakes
     registry.install()
 
diff --git a/portal/tests/test_config.py b/portal/tests/test_config.py
index 4177845..0977a2f 100644
--- a/portal/tests/test_config.py
+++ b/portal/tests/test_config.py
@@ -140,3 +140,41 @@ def test_oidc_addresses_must_be_https_origins(valid_env, name, value):
 def test_a_plain_http_origin_is_allowed_only_in_debug(valid_env):
     env = {**valid_env, "PUBLIC_BASE_URL": "http://localhost:8000"}
     assert load_config({**env, "DEBUG": "true"}).oidc.public_base_url == "http://localhost:8000"
+
+
+def test_smtp_settings_default_to_starttls_on_587_and_hide_the_password(valid_env):
+    smtp = load_config(valid_env).smtp
+    assert (smtp.host, smtp.port, smtp.security) == ("mail.example.test", 587, "starttls")
+    assert smtp.sender == "Portal <portal@example.test>"
+    assert "mail-password" not in repr(smtp)
+
+
+def test_smtp_ssl_defaults_to_port_465_and_the_port_can_be_set(valid_env):
+    assert load_config({**valid_env, "SMTP_SECURITY": "SSL"}).smtp.port == 465
+    assert load_config({**valid_env, "SMTP_PORT": "2525"}).smtp.port == 2525
+
+
+@pytest.mark.parametrize(
+    ("name", "value"),
+    [
+        ("SMTP_HOST", "smtp://mail.example.test"),
+        ("SMTP_HOST", "mail.example.test:587"),
+        ("SMTP_SECURITY", "plain"),
+        ("SMTP_PORT", "abc"),
+        ("SMTP_PORT", "0"),
+        ("SMTP_PORT", "70000"),
+        ("MAIL_FROM", "not-an-address"),
+        ("MAIL_FROM", "a@b.test\r\nBcc: x@evil.test"),
+        ("MAIL_FROM", "@example.test"),
+    ],
+)
+def test_invalid_smtp_settings_are_refused(valid_env, name, value):
+    with pytest.raises(ConfigError, match=name):
+        load_config({**valid_env, name: value})
+
+
+@pytest.mark.parametrize("name", ["SMTP_HOST", "SMTP_USERNAME", "SMTP_PASSWORD", "MAIL_FROM"])
+def test_the_mail_settings_are_required(valid_env, name):
+    del valid_env[name]
+    with pytest.raises(ConfigError, match=name):
+        load_config(valid_env)
diff --git a/portal/tests/test_mailer.py b/portal/tests/test_mailer.py
new file mode 100644
index 0000000..6b9b4aa
--- /dev/null
+++ b/portal/tests/test_mailer.py
@@ -0,0 +1,263 @@
+"""The outbox: queue, send, retry, rate limit and restart safety (AD-11)."""
+
+import logging
+from datetime import timedelta
+
+import pytest
+from django.core.management import call_command
+from django.db import transaction
+from django.utils import timezone
+
+from portal.mailer import services
+from portal.mailer.models import OutboxMail
+
+pytestmark = pytest.mark.django_db(transaction=True)
+
+Status = OutboxMail.Status
+
+
+def queue(recipient="lena@example.test", n=1):
+    return [services.enqueue("test", recipient) for _ in range(n)][-1]
+
+
+# -- queueing -----------------------------------------
+
+
+def test_enqueue_renders_the_mail_in_formal_german():
+    mail = queue()
+    assert mail.status == Status.QUEUED and mail.attempts == 0
+    assert mail.subject == "Test-E-Mail vom Portal"
+    assert "Wenn Sie sie lesen können" in mail.body_text
+
+
+def test_the_language_of_the_request_does_not_change_the_mail():
+    from django.utils import translation
+
+    with translation.override("en"):
+        assert queue().subject == "Test-E-Mail vom Portal"
+
+
+@pytest.mark.parametrize(
+    "address",
+    ["", "nobody", "a@b", "a b@example.test", "a@example.test\r\nBcc: x@evil.test", "<a@b.test>"],
+)
+def test_an_unusable_address_is_refused_and_nothing_is_queued(address):
+    with pytest.raises(ValueError, match="e-mail address"):
+        services.enqueue("test", address)
+    assert OutboxMail.objects.count() == 0
+
+
+def test_a_rolled_back_change_queues_nothing():
+    with pytest.raises(RuntimeError), transaction.atomic():
+        queue()
+        raise RuntimeError("the change failed")
+    assert OutboxMail.objects.count() == 0
+
+
+# -- sending -----------------------------------------
+
+
+def test_flush_sends_a_queued_mail_and_removes_its_text(adapters):
+    mail = queue()
+    result = services.flush()
+    mail.refresh_from_db()
+    assert (result.sent, result.retried, result.failed) == (1, 0, 0)
+    assert mail.status == Status.SENT and mail.sent_at and mail.attempts == 1
+    assert mail.body_text == ""  # a one-time link must not stay in the database
+    sent = adapters.mailer.sent[0]
+    assert sent.recipient == "lena@example.test" and sent.sender == "Portal <portal@example.test>"
+    assert "Test-E-Mail" in sent.subject and "Test-E-Mail" in sent.body_text
+
+
+def test_a_mail_is_never_sent_twice(adapters):
+    queue()
+    services.flush()
+    services.flush()
+    services.flush(timezone.now() + timedelta(days=1))
+    assert len(adapters.mailer.sent) == 1
+
+
+def test_a_mail_that_is_not_due_yet_waits(adapters):
+    mail = queue()
+    later = timezone.now() + timedelta(hours=1)
+    OutboxMail.objects.filter(pk=mail.pk).update(next_attempt_at=later)
+    services.flush()
+    assert adapters.mailer.sent == []
+
+
+def test_mails_are_sent_in_the_order_they_were_queued(adapters):
+    for name in ("a", "b", "c"):
+        queue(f"{name}@example.test")
+    services.flush()
+    assert [m.recipient for m in adapters.mailer.sent] == [f"{n}@example.test" for n in "abc"]
+
+
+# -- failures -----------------------------------------
+
+
+def test_a_temporary_failure_is_retried_later_with_a_growing_wait(adapters):
+    mail = queue()
+    adapters.mailer.unavailable = True
+    now = timezone.now()
+    waits = []
+    for attempt in range(1, 5):
+        result = services.flush(now)
+        mail.refresh_from_db()
+        assert result.retried == 1 and mail.status == Status.QUEUED and mail.attempts == attempt
+        assert mail.last_error
+        waits.append(mail.next_attempt_at - now)
+        now = mail.next_attempt_at
+    assert waits == [timedelta(seconds=s) for s in services.BACKOFF_SECONDS]
+    assert waits == sorted(waits)
+
+
+def test_a_retry_before_the_wait_is_over_does_nothing(adapters):
+    mail = queue()
+    adapters.mailer.unavailable = True
+    now = timezone.now()
+    services.flush(now)
+    attempts = adapters.mailer.attempts
+    services.flush(now + timedelta(seconds=30))
+    assert adapters.mailer.attempts == attempts
+    mail.refresh_from_db()
+    assert mail.attempts == 1
+
+
+def test_a_mail_that_works_on_a_retry_is_sent(adapters):
+    mail = queue()
+    adapters.mailer.unavailable = True
+    now = timezone.now()
+    services.flush(now)
+    adapters.mailer.unavailable = False
+    mail.refresh_from_db()
+    result = services.flush(mail.next_attempt_at)
+    mail.refresh_from_db()
+    assert result.sent == 1 and mail.status == Status.SENT and mail.attempts == 2
+
+
+def test_after_the_last_attempt_the_mail_is_failed_and_kept_for_the_admin(adapters):
+    mail = queue()
+    adapters.mailer.unavailable = True
+    now = timezone.now()
+    for _ in range(services.MAX_ATTEMPTS):
+        services.flush(now)
+        mail.refresh_from_db()
+        now = mail.next_attempt_at
+    assert mail.status == Status.FAILED and mail.attempts == services.MAX_ATTEMPTS
+    assert mail.recipient == "lena@example.test" and mail.last_error and mail.body_text == ""
+    attempts = adapters.mailer.attempts
+    services.flush(now + timedelta(days=1))
+    assert adapters.mailer.attempts == attempts  # no further tries
+
+
+def test_a_permanent_refusal_fails_at_once_without_retries(adapters):
+    mail = queue("gone@example.test")
+    adapters.mailer.rejected.add("gone@example.test")
+    result = services.flush()
+    mail.refresh_from_db()
+    assert result.failed == 1 and mail.status == Status.FAILED and mail.attempts == 1
+    assert "550" in mail.last_error
+
+
+def test_one_refused_mail_does_not_block_the_others(adapters):
+    queue("gone@example.test")
+    queue("lena@example.test")
+    adapters.mailer.rejected.add("gone@example.test")
+    result = services.flush()
+    assert (result.sent, result.failed) == (1, 1)
+
+
+def test_a_dead_server_is_not_tried_for_every_mail_in_the_queue(adapters):
+    for i in range(10):
+        queue(f"u{i}@example.test")
+    adapters.mailer.unavailable = True
+    services.flush()
+    assert adapters.mailer.attempts == services.STOP_AFTER_CONSECUTIVE_OUTAGES
+
+
+# -- rate limit -----------------------------------------
+
+
+def test_no_more_than_the_rate_limit_is_sent_per_minute(adapters):
+    for i in range(services.RATE_PER_MINUTE + 5):
+        queue(f"u{i}@example.test")
+    now = timezone.now()
+    assert services.flush(now).sent == services.RATE_PER_MINUTE
+    assert services.flush(now + timedelta(seconds=30)).sent == 0
+    assert services.flush(now + timedelta(seconds=61)).sent == 5
+    assert len(adapters.mailer.sent) == services.RATE_PER_MINUTE + 5
+
+
+# -- restarts -----------------------------------------
+
+
+def test_a_mail_cut_off_while_sending_is_given_up_not_sent_again(adapters):
+    mail = queue()
+    now = timezone.now()
+    OutboxMail.objects.filter(pk=mail.pk).update(
+        status=Status.SENDING, claimed_at=now - timedelta(seconds=services.LEASE_SECONDS + 1)
+    )
+    result = services.flush(now)
+    mail.refresh_from_db()
+    assert mail.status == Status.FAILED and "unknown" in mail.last_error
+    assert result.sent == 0 and adapters.mailer.sent == []
+
+
+def test_a_mail_being_sent_right_now_is_left_alone(adapters):
+    mail = queue()
+    now = timezone.now()
+    OutboxMail.objects.filter(pk=mail.pk).update(status=Status.SENDING, claimed_at=now)
+    services.flush(now)
+    mail.refresh_from_db()
+    assert mail.status == Status.SENDING and adapters.mailer.sent == []
+
+
+def test_a_row_taken_by_another_run_is_skipped(adapters, monkeypatch):
+    mail = queue()
+    real = OutboxMail.objects.filter
+
+    def take_first(*args, **kwargs):
+        # The moment the claim is attempted, another run has already taken the row.
+        if kwargs.get("pk") == mail.pk:
+            real(pk=mail.pk).update(status=Status.SENDING)
+        return real(*args, **kwargs)
+
+    monkeypatch.setattr(OutboxMail.objects, "filter", take_first)
+    assert services.flush().sent == 0
+    assert adapters.mailer.sent == []
+
+
+# -- privacy -----------------------------------------
+
+
+def test_logs_name_the_row_but_not_the_recipient_or_text(adapters, caplog):
+    queue("secret.person@example.test")
+    adapters.mailer.unavailable = True
+    with caplog.at_level(logging.DEBUG):
+        services.flush()
+    assert "not sent" in caplog.text
+    assert "secret.person" not in caplog.text and "Test-E-Mail" not in caplog.text
+
+
+# -- the test command -----------------------------------------
+
+
+def test_the_test_command_sends_a_mail_now(adapters, capsys):
+    call_command("send_test_mail", "lena@example.test")
+    assert "sent" in capsys.readouterr().out
+    assert [m.recipient for m in adapters.mailer.sent] == ["lena@example.test"]
+
+
+def test_the_test_command_reports_a_failure(adapters, capsys):
+    adapters.mailer.unavailable = True
+    with pytest.raises(SystemExit) as stop:
+        call_command("send_test_mail", "lena@example.test")
+    assert stop.value.code == 1
+    assert "retried" in capsys.readouterr().out
+
+
+def test_the_test_command_refuses_a_bad_address(adapters):
+    from django.core.management.base import CommandError
+
+    with pytest.raises(CommandError):
+        call_command("send_test_mail", "not-an-address")
diff --git a/portal/tests/test_scheduler.py b/portal/tests/test_scheduler.py
new file mode 100644
index 0000000..d9a37ef
--- /dev/null
+++ b/portal/tests/test_scheduler.py
@@ -0,0 +1,104 @@
+"""The scheduler: one tick runs the jobs and records each run (AD-12)."""
+
+import threading
+from datetime import timedelta
+
+import pytest
+from django.utils import timezone
+
+from portal.mailer import services as mailer
+from portal.scheduler import services
+from portal.scheduler.models import JobRun
+from portal.scheduler.runner import Runner
+
+pytestmark = pytest.mark.django_db(transaction=True)
+
+
+def test_a_tick_runs_the_mail_job_and_records_the_run(adapters):
+    mailer.enqueue("test", "lena@example.test")
+    services.tick()
+    assert len(adapters.mailer.sent) == 1
+    run = JobRun.objects.get(job="mail.flush")
+    assert run.status == JobRun.Status.OK and run.finished_at
+    assert run.detail == "sent=1 retried=0 failed=0"
+
+
+def test_an_idle_tick_is_recorded_too_and_repeating_it_is_harmless(adapters):
+    services.tick()
+    services.tick()
+    assert JobRun.objects.filter(job="mail.flush").count() == 2
+    assert adapters.mailer.sent == []
+
+
+def test_a_restart_sends_nothing_twice(adapters):
+    mailer.enqueue("test", "lena@example.test")
+    services.tick()
+    services.tick(timezone.now() + timedelta(minutes=5))  # "after a restart"
+    assert len(adapters.mailer.sent) == 1
+
+
+def test_a_failing_job_is_recorded_and_the_others_still_run():
+    ran = []
+
+    def broken(now):
+        raise RuntimeError("secret detail that must not be stored")
+
+    jobs = (
+        services.Job("first", lambda now: ran.append("first") or "fine"),
+        services.Job("broken", broken),
+        services.Job("last", lambda now: ran.append("last") or "also fine"),
+    )
+    services.tick(jobs=jobs)
+    assert ran == ["first", "last"]
+    broken_run = JobRun.objects.get(job="broken")
+    assert broken_run.status == JobRun.Status.ERROR and broken_run.detail == "RuntimeError"
+    assert JobRun.objects.get(job="last").status == JobRun.Status.OK
+
+
+def test_old_run_records_are_removed():
+    now = timezone.now()
+    JobRun.objects.create(job="x", started_at=now - timedelta(days=services.KEEP_RUNS_DAYS + 1))
+    JobRun.objects.create(job="x", started_at=now - timedelta(days=1))
+    services.tick(now, jobs=())
+    assert JobRun.objects.filter(job="x").count() == 1
+
+
+# -- the thread -----------------------------------------
+
+
+def test_the_thread_ticks_repeatedly_and_stops():
+    ticked = threading.Semaphore(0)
+    runner = Runner(tick=ticked.release, interval=0.01)
+    runner.start()
+    assert ticked.acquire(timeout=2) and ticked.acquire(timeout=2)
+    runner.stop()
+    assert not runner._thread.is_alive()
+
+
+def test_a_failing_tick_does_not_stop_the_thread():
+    calls = threading.Semaphore(0)
+
+    def tick():
+        calls.release()
+        raise RuntimeError("boom")
+
+    runner = Runner(tick=tick, interval=0.01)
+    runner.start()
+    assert calls.acquire(timeout=2) and calls.acquire(timeout=2)
+    runner.stop()
+
+
+def test_starting_twice_runs_only_one_thread():
+    runner = Runner(tick=lambda: None, interval=0.05)
+    runner.start()
+    first = runner._thread
+    runner.start()
+    assert runner._thread is first
+    runner.stop()
+    assert sum(1 for t in threading.enumerate() if t.name == "scheduler") == 0
+
+
+def test_the_default_interval_is_thirty_seconds():
+    from portal.scheduler.runner import TICK_SECONDS, runner
+
+    assert TICK_SECONDS == 30 and runner._interval == 30
diff --git a/portal/tests/test_smtp_mailer.py b/portal/tests/test_smtp_mailer.py
new file mode 100644
index 0000000..bc0c5f2
--- /dev/null
+++ b/portal/tests/test_smtp_mailer.py
@@ -0,0 +1,180 @@
+"""The SMTP adapter against a stand-in for `smtplib`; no network."""
+
+import smtplib
+import ssl
+
+import pytest
+
+from portal.adapters.mail import MailMessage, MailRejected, MailUnavailable, SmtpMailer
+from portal.config.env import SmtpConfig
+
+MESSAGE = MailMessage(
+    sender="Portal <portal@example.test>",
+    recipient="lena@example.test",
+    subject="Hallo Lena",
+    body_text="Guten Tag, schöne Grüße\n",
+)
+
+
+def config(security="starttls", port=587):
+    return SmtpConfig("mail.example.test", port, security, "box@example.test", "pw", "a@b.test")
+
+
+class FakeSmtpModule:
+    """Looks like the `smtplib` module and records what the adapter does."""
+
+    SMTPException = smtplib.SMTPException
+    SMTPAuthenticationError = smtplib.SMTPAuthenticationError
+    SMTPRecipientsRefused = smtplib.SMTPRecipientsRefused
+    SMTPResponseException = smtplib.SMTPResponseException
+
+    def __init__(self):
+        self.calls = []
+        self.fail_at = {}  # step name -> exception to raise
+        self.sent = []
+        self.connect_error = None
+
+    def _connection(self, kind, args, kwargs):
+        if self.connect_error:
+            raise self.connect_error
+        module = self
+        module.calls.append((kind, args, kwargs))
+
+        class Connection:
+            def _step(self, name, *a, **k):
+                module.calls.append((name, a, k))
+                if name in module.fail_at:
+                    raise module.fail_at[name]
+
+            def ehlo(self):
+                self._step("ehlo")
+
+            def starttls(self, context=None):
+                self._step("starttls", context=context)
+
+            def login(self, user, password):
+                self._step("login", user, password)
+
+            def send_message(self, message):
+                self._step("send_message")
+                module.sent.append(message)
+
+            def quit(self):
+                self._step("quit")
+
+            def close(self):
+                module.calls.append(("close", (), {}))
+
+        return Connection()
+
+    def SMTP(self, *args, **kwargs):  # noqa: N802
+        return self._connection("SMTP", args, kwargs)
+
+    def SMTP_SSL(self, *args, **kwargs):  # noqa: N802
+        return self._connection("SMTP_SSL", args, kwargs)
+
+    def names(self):
+        return [c[0] for c in self.calls]
+
+
+@pytest.fixture
+def smtp():
+    return FakeSmtpModule()
+
+
+def test_starttls_encrypts_before_the_login(smtp):
+    SmtpMailer(config("starttls"), smtp).send(MESSAGE)
+    assert smtp.names() == ["SMTP", "ehlo", "starttls", "ehlo", "login", "send_message", "quit"]
+    context = [c for c in smtp.calls if c[0] == "starttls"][0][2]["context"]
+    assert context.verify_mode == ssl.CERT_REQUIRED and context.check_hostname
+
+
+def test_ssl_mode_uses_an_encrypted_connection_from_the_start(smtp):
+    SmtpMailer(config("ssl", 465), smtp).send(MESSAGE)
+    assert smtp.names() == ["SMTP_SSL", "ehlo", "login", "send_message", "quit"]
+    kind, args, kwargs = smtp.calls[0]
+    assert args == ("mail.example.test", 465) and kwargs["timeout"] > 0
+    assert kwargs["context"].verify_mode == ssl.CERT_REQUIRED
+
+
+def test_the_login_uses_the_configured_mailbox(smtp):
+    SmtpMailer(config(), smtp).send(MESSAGE)
+    assert ("login", ("box@example.test", "pw"), {}) in smtp.calls
+
+
+def test_the_message_is_a_utf8_plain_text_mail_with_the_usual_headers(smtp):
+    SmtpMailer(config(), smtp).send(MESSAGE)
+    email = smtp.sent[0]
+    assert email["From"] == "Portal <portal@example.test>"
+    assert email["To"] == "lena@example.test"
+    assert email["Subject"] == "Hallo Lena"
+    assert email["Date"] and email["Message-ID"].endswith("@mail.example.test>")
+    assert email.get_content_type() == "text/plain"
+    assert "schöne Grüße" in email.get_content()
+
+
+@pytest.mark.parametrize(
+    "bad",
+    [
+        {"subject": "Hi\r\nBcc: x@evil.test"},
+        {"recipient": "a@example.test\r\nBcc: x@evil.test"},
+        {"recipient": "a@example.test\nBcc: x@evil.test"},
+    ],
+)
+def test_a_line_break_in_a_header_cannot_add_headers(smtp, bad):
+    message = MailMessage(**{**MESSAGE.__dict__, **bad})
+    with pytest.raises(MailRejected):
+        SmtpMailer(config(), smtp).send(message)
+    assert smtp.sent == []
+
+
+@pytest.mark.parametrize(
+    ("error", "expected"),
+    [
+        (smtplib.SMTPResponseException(421, b"busy"), MailUnavailable),
+        (smtplib.SMTPResponseException(450, b"try later"), MailUnavailable),
+        (smtplib.SMTPResponseException(550, b"no such user"), MailRejected),
+        (smtplib.SMTPResponseException(554, b"refused"), MailRejected),
+        (smtplib.SMTPServerDisconnected("gone"), MailUnavailable),
+        (TimeoutError("slow"), MailUnavailable),
+        (ssl.SSLError("bad certificate"), MailUnavailable),
+        (
+            smtplib.SMTPRecipientsRefused({"lena@example.test": (550, b"unknown")}),
+            MailRejected,
+        ),
+        (
+            smtplib.SMTPRecipientsRefused({"lena@example.test": (452, b"mailbox full")}),
+            MailUnavailable,
+        ),
+    ],
+)
+def test_server_answers_are_mapped_to_temporary_or_permanent(smtp, error, expected):
+    smtp.fail_at["send_message"] = error
+    with pytest.raises(expected):
+        SmtpMailer(config(), smtp).send(MESSAGE)
+
+
+def test_a_refused_login_is_temporary_so_a_fixed_password_works_on_the_retry(smtp):
+    smtp.fail_at["login"] = smtplib.SMTPAuthenticationError(535, b"bad credentials")
+    with pytest.raises(MailUnavailable):
+        SmtpMailer(config(), smtp).send(MESSAGE)
+    assert "close" in smtp.names() and "send_message" not in smtp.names()
+
+
+def test_an_unreachable_server_is_temporary(smtp):
+    smtp.connect_error = ConnectionRefusedError("no")
+    with pytest.raises(MailUnavailable):
+        SmtpMailer(config(), smtp).send(MESSAGE)
+
+
+def test_a_failing_quit_does_not_hide_a_successful_send(smtp):
+    smtp.fail_at["quit"] = smtplib.SMTPServerDisconnected("closed")
+    SmtpMailer(config(), smtp).send(MESSAGE)
+    assert len(smtp.sent) == 1
+
+
+def test_errors_never_contain_the_recipient_or_the_server_text(smtp):
+    smtp.fail_at["send_message"] = smtplib.SMTPResponseException(550, b"lena@example.test unknown")
+    with pytest.raises(MailRejected) as caught:
+        SmtpMailer(config(), smtp).send(MESSAGE)
+    assert "lena" not in str(caught.value) and "unknown" not in str(caught.value)
diff --git a/portal/tests/test_translations.py b/portal/tests/test_translations.py
index 239b41c..be477b8 100644
--- a/portal/tests/test_translations.py
+++ b/portal/tests/test_translations.py
@@ -17,7 +17,8 @@ PY_CALL = re.compile(r"""(?<![\w.])(?:_|gettext|gettext_lazy)\(\s*(?:"([^"]+)"|'
 
 def msgids_in_code() -> set[str]:
     found = set()
-    for template in (PORTAL / "templates").rglob("*.html"):
+    templates = [*(PORTAL / "templates").rglob("*.html"), *(PORTAL / "templates").rglob("*.txt")]
+    for template in templates:
         text = template.read_text(encoding="utf-8")
         found.update(a or b for a, b in TRANS_TAG.findall(text))
         found.update(VARIABLE.sub(r"%(\1)s", body).strip() for body in BLOCKTRANS.findall(text))
diff --git a/pyproject.toml b/pyproject.toml
index 5683b9a..362f674 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -44,6 +44,10 @@ env = [
     "OIDC_CLIENT_ID=portal-client",
     "OIDC_CLIENT_SECRET=test-only-client-secret",
     "PUBLIC_BASE_URL=https://portal.example.test",
+    "SMTP_HOST=mail.example.test",
+    "SMTP_USERNAME=portal@example.test",
+    "SMTP_PASSWORD=test-only-mail-password",
+    "MAIL_FROM=Portal <portal@example.test>",
 ]
 
 [tool.ruff]