images/postfix-pgsql/Dockerfile

@@ -0,0 +1,38 @@
+# =============================================================================
+# Postfix + PostgreSQL Relay/MTA Image
+#
+# A pure SMTP relay/MTA: receives inbound mail and forwards it based on
+# PostgreSQL-backed relay_domains/transport_maps lookups, equivalent to the
+# Postfix setup described in the SimpleLogin self-hosting documentation
+# (https://github.com/simple-login/app). No domain, hostname, or database
+# credentials are baked into the image; everything is templated from
+# environment variables at container startup. This image has no knowledge
+# of what consumes the relayed mail.
+# =============================================================================
+
+# POSTFIX_VERSION pins the Debian base image tag (e.g. "12-slim"), which in
+# turn pins the postfix/postfix-pgsql package versions available via apt.
+ARG POSTFIX_VERSION=12-slim
+FROM debian:${POSTFIX_VERSION}
+
+LABEL maintainer="Damien Arnodo"
+LABEL description="Postfix SMTP relay/MTA with PostgreSQL-backed relay_domains and transport_maps lookups"
+
+RUN echo "postfix postfix/main_mailer_type select No configuration" | debconf-set-selections \
+    && echo "postfix postfix/mailname string localhost" | debconf-set-selections \
+    && apt-get update \
+    && apt-get install -y --no-install-recommends \
+        postfix \
+        postfix-pgsql \
+        gettext-base \
+        openssl \
+        ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY templates/ /etc/postfix/templates/
+COPY docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
+RUN chmod +x /usr/local/bin/docker-entrypoint.sh
+
+EXPOSE 25
+
+ENTRYPOINT ["docker-entrypoint.sh"]

images/postfix-pgsql/POSTFIX_VERSION

@@ -0,0 +1 @@
+12-slim

images/postfix-pgsql/README.md

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+# Postfix PostgreSQL Relay Image
+
+A Postfix SMTP relay/MTA whose relay and transport decisions are driven by
+PostgreSQL lookup maps instead of static config. It receives inbound mail and
+forwards it to an internal SMTP target after checking the recipient's domain
+against a database — it has no knowledge of, and makes no assumptions about,
+what consumes the mail downstream.
+
+This mirrors the Postfix setup described in the SimpleLogin self-hosting
+documentation (`postfix` + `postfix-pgsql`, a `relay_domains` PostgreSQL map,
+and a `transport_maps` PostgreSQL map): https://github.com/simple-login/app
+
+No domain, hostname, or database credential is hardcoded in the image.
+Everything is templated from environment variables by
+`docker-entrypoint.sh` at container startup, then Postfix is started in the
+foreground (`postfix start-fg`) so it runs correctly under Docker's process
+supervision.
+
+## How it works
+
+On startup, the entrypoint renders three files from templates under
+`/etc/postfix/templates/`:
+
+- `/etc/postfix/main.cf` — core Postfix configuration.
+- `/etc/postfix/pgsql-relay-domains.cf` — PostgreSQL lookup that tells
+  Postfix which domains it should relay mail for.
+- `/etc/postfix/pgsql-transport-maps.cf` — PostgreSQL lookup that tells
+  Postfix where to forward accepted mail (the internal SMTP relay target).
+
+Chroot is disabled for all Postfix services via `postconf -F '*/*/chroot = n'`
+on every startup. Postfix's chrooted child processes (smtpd, trivial-rewrite,
+etc.) lack access to `/etc/resolv.conf` inside the chroot jail, so they cannot
+resolve Docker-internal hostnames — causing every PostgreSQL lookup to fail with
+`451 4.3.0 Temporary lookup failure`. Disabling chroot is the standard remedy
+in containerised deployments.
+
+## Environment variables
+
+### Required
+
+| Variable | Description | Example |
+|----------|--------------|---------|
+| `MAIL_DOMAIN` | Mail domain this relay handles (`mydomain`/`myorigin` in `main.cf`). | `example.com` |
+| `MYHOSTNAME` | Hostname of this relay, used as Postfix's `myhostname` and as the MX target for `MAIL_DOMAIN`. | `mx1.example.com` |
+| `POSTGRES_HOST` | Hostname of the PostgreSQL server holding the lookup tables. | `postgres` |
+| `POSTGRES_PORT` | PostgreSQL port. | `5432` |
+| `POSTGRES_USER` | PostgreSQL user used for the lookup queries. | `postfix` |
+| `POSTGRES_PASSWORD` | PostgreSQL password for `POSTGRES_USER`. | `change-me` |
+| `POSTGRES_DB` | PostgreSQL database name. | `relaydb` |
+| `SMTP_RELAY_HOST` | Internal SMTP host that accepted mail is forwarded to after the relay-domains lookup matches. | `app-internal` |
+| `SMTP_RELAY_PORT` | Port of the internal SMTP relay target. | `2525` |
+
+### Optional
+
+| Variable | Description |
+|----------|--------------|
+| `TLS_CERT_FILE` | Absolute path (inside the container) to a TLS certificate to use for `smtpd_tls_cert_file`. If unset, a self-signed certificate is generated on first start. |
+| `TLS_KEY_FILE` | Absolute path (inside the container) to the private key matching `TLS_CERT_FILE`. Must be set together with `TLS_CERT_FILE`. |
+
+The PostgreSQL lookup tables are expected to expose at least a
+`relay_domain(domain)` table; both lookups query it by recipient domain.
+
+## TLS certificates
+
+By default, if `TLS_CERT_FILE`/`TLS_KEY_FILE` are not provided, the
+entrypoint generates a self-signed certificate at
+`/etc/postfix/ssl/snakeoil.{pem,key}` on first start (matching the
+self-signed fallback used in the upstream docs) and reuses it on subsequent
+restarts if that path is kept on a persistent volume.
+
+To use your own certificate instead, mount it into the container and point
+`TLS_CERT_FILE`/`TLS_KEY_FILE` at the mounted paths, e.g.:
+
+```bash
+docker run \
+  -v /path/to/fullchain.pem:/certs/fullchain.pem:ro \
+  -v /path/to/privkey.pem:/certs/privkey.pem:ro \
+  -e TLS_CERT_FILE=/certs/fullchain.pem \
+  -e TLS_KEY_FILE=/certs/privkey.pem \
+  ...
+```
+
+## Usage
+
+### `docker run`
+
+```bash
+docker run -d \
+  -p 25:25 \
+  -e MAIL_DOMAIN=example.com \
+  -e MYHOSTNAME=mx1.example.com \
+  -e POSTGRES_HOST=postgres \
+  -e POSTGRES_PORT=5432 \
+  -e POSTGRES_USER=postfix \
+  -e POSTGRES_PASSWORD=change-me \
+  -e POSTGRES_DB=relaydb \
+  -e SMTP_RELAY_HOST=app-internal \
+  -e SMTP_RELAY_PORT=2525 \
+  gitea.arnodo.fr/damien/postfix-pgsql:latest
+```
+
+### Docker Compose
+
+```yaml
+services:
+  postfix:
+    image: gitea.arnodo.fr/damien/postfix-pgsql:latest
+    ports:
+      - "25:25"
+    environment:
+      MAIL_DOMAIN: example.com
+      MYHOSTNAME: mx1.example.com
+      POSTGRES_HOST: postgres
+      POSTGRES_PORT: "5432"
+      POSTGRES_USER: postfix
+      POSTGRES_PASSWORD: change-me
+      POSTGRES_DB: relaydb
+      SMTP_RELAY_HOST: app-internal
+      SMTP_RELAY_PORT: "2525"
+```
+
+## Version management
+
+The Debian base image tag is set in `POSTFIX_VERSION` (e.g. `12-slim`),
+which also pins the `postfix`/`postfix-pgsql` package versions available via
+`apt` for that Debian release. To change it:
+
+1. Edit `POSTFIX_VERSION` with the desired Debian tag.
+2. Commit and push.
+3. The CI builds the image with that base and tags it with both `latest` and
+   the value of `POSTFIX_VERSION`.
+
+## Reference
+
+- Upstream Postfix + PostgreSQL setup this image is based on:
+  https://github.com/simple-login/app

images/postfix-pgsql/docker-entrypoint.sh

@@ -0,0 +1,68 @@
+#!/bin/bash
+# =============================================================================
+# Renders Postfix config templates from environment variables and starts
+# Postfix in the foreground.
+# =============================================================================
+set -euo pipefail
+
+TEMPLATE_DIR="/etc/postfix/templates"
+SSL_DIR="/etc/postfix/ssl"
+
+require_var() {
+    local name="$1"
+    if [ -z "${!name:-}" ]; then
+        echo "ERROR: required environment variable ${name} is not set" >&2
+        exit 1
+    fi
+}
+
+for var in MAIL_DOMAIN MYHOSTNAME \
+    POSTGRES_HOST POSTGRES_PORT POSTGRES_USER POSTGRES_PASSWORD POSTGRES_DB \
+    SMTP_RELAY_HOST SMTP_RELAY_PORT; do
+    require_var "$var"
+done
+
+# TLS: use mounted cert/key if provided, otherwise generate a self-signed
+# "snakeoil" certificate on first start, matching the upstream docs' approach.
+mkdir -p "$SSL_DIR"
+if [ -n "${TLS_CERT_FILE:-}" ] && [ -n "${TLS_KEY_FILE:-}" ]; then
+    export SMTPD_TLS_CERT_FILE="$TLS_CERT_FILE"
+    export SMTPD_TLS_KEY_FILE="$TLS_KEY_FILE"
+else
+    export SMTPD_TLS_CERT_FILE="${SSL_DIR}/snakeoil.pem"
+    export SMTPD_TLS_KEY_FILE="${SSL_DIR}/snakeoil.key"
+    if [ ! -f "$SMTPD_TLS_CERT_FILE" ] || [ ! -f "$SMTPD_TLS_KEY_FILE" ]; then
+        echo "No TLS_CERT_FILE/TLS_KEY_FILE provided, generating a self-signed certificate"
+        openssl req -x509 -nodes -days 3650 \
+            -newkey rsa:2048 \
+            -subj "/CN=${MYHOSTNAME}" \
+            -keyout "$SMTPD_TLS_KEY_FILE" \
+            -out "$SMTPD_TLS_CERT_FILE"
+        chmod 600 "$SMTPD_TLS_KEY_FILE"
+    fi
+fi
+
+render() {
+    local template="$1"
+    local destination="$2"
+    envsubst '${MAIL_DOMAIN} ${MYHOSTNAME} ${SMTPD_TLS_CERT_FILE} ${SMTPD_TLS_KEY_FILE} ${POSTGRES_HOST} ${POSTGRES_PORT} ${POSTGRES_USER} ${POSTGRES_PASSWORD} ${POSTGRES_DB} ${SMTP_RELAY_HOST} ${SMTP_RELAY_PORT}' \
+        < "$template" > "$destination"
+}
+
+render "${TEMPLATE_DIR}/main.cf.template" /etc/postfix/main.cf
+render "${TEMPLATE_DIR}/pgsql-relay-domains.cf.template" /etc/postfix/pgsql-relay-domains.cf
+render "${TEMPLATE_DIR}/pgsql-transport-maps.cf.template" /etc/postfix/pgsql-transport-maps.cf
+
+# The pgsql lookup config files embed the database password; restrict access.
+chown root:postfix /etc/postfix/pgsql-relay-domains.cf /etc/postfix/pgsql-transport-maps.cf
+chmod 640 /etc/postfix/pgsql-relay-domains.cf /etc/postfix/pgsql-transport-maps.cf
+
+postfix check
+
+# Disable chroot for all master.cf services so child processes (smtpd,
+# trivial-rewrite, etc.) can resolve Docker-internal hostnames via the host's
+# /etc/resolv.conf. Without this, chrooted processes have no DNS and every
+# pgsql lookup returns "451 4.3.0 Temporary lookup failure".
+postconf -F '*/*/chroot = n'
+
+exec /usr/sbin/postfix start-fg

images/postfix-pgsql/templates/main.cf.template

@@ -0,0 +1,39 @@
+# =============================================================================
+# Postfix main.cf template
+#
+# Rendered at container startup by docker-entrypoint.sh, with values
+# substituted from environment variables. See README.md for the full list
+# of supported variables.
+# =============================================================================
+
+myhostname = ${MYHOSTNAME}
+mydomain = ${MAIL_DOMAIN}
+myorigin = $mydomain
+mydestination =
+inet_interfaces = all
+inet_protocols = ipv4
+
+# Dynamic relay/transport decisions backed by PostgreSQL lookup maps.
+relay_domains = pgsql:/etc/postfix/pgsql-relay-domains.cf
+transport_maps = pgsql:/etc/postfix/pgsql-transport-maps.cf
+
+# This instance only relays mail for the domains returned by relay_domains;
+# it does not accept mail for arbitrary destinations.
+smtpd_relay_restrictions = permit_mynetworks, reject_unauth_destination
+mynetworks = 127.0.0.0/8, [::1]/128
+
+# TLS
+smtpd_tls_cert_file = ${SMTPD_TLS_CERT_FILE}
+smtpd_tls_key_file = ${SMTPD_TLS_KEY_FILE}
+smtpd_use_tls = yes
+smtpd_tls_security_level = may
+smtp_tls_security_level = may
+
+# Log to stdout/stderr so `docker logs` captures Postfix activity directly,
+# without needing a syslog daemon inside the container.
+maillog_file = /dev/stdout
+
+biff = no
+append_dot_mydomain = no
+readme_directory = no
+compatibility_level = 3.6

images/postfix-pgsql/templates/pgsql-relay-domains.cf.template

@@ -0,0 +1,12 @@
+# =============================================================================
+# Postfix pgsql_table lookup: relay_domains
+#
+# Returns the domain itself when Postfix should relay mail for it.
+# Rendered at container startup from environment variables.
+# =============================================================================
+
+user = ${POSTGRES_USER}
+password = ${POSTGRES_PASSWORD}
+hosts = ${POSTGRES_HOST}:${POSTGRES_PORT}
+dbname = ${POSTGRES_DB}
+query = SELECT domain FROM relay_domain WHERE domain='%s'

images/postfix-pgsql/templates/pgsql-transport-maps.cf.template

@@ -0,0 +1,15 @@
+# =============================================================================
+# Postfix pgsql_table lookup: transport_maps
+#
+# Returns the internal SMTP relay target that accepted mail gets forwarded
+# to once a recipient domain matches relay_domains. The target itself is
+# baked into the query from SMTP_RELAY_HOST/SMTP_RELAY_PORT at startup; this
+# image has no further knowledge of what consumes the mail downstream.
+# Rendered at container startup from environment variables.
+# =============================================================================
+
+user = ${POSTGRES_USER}
+password = ${POSTGRES_PASSWORD}
+hosts = ${POSTGRES_HOST}:${POSTGRES_PORT}
+dbname = ${POSTGRES_DB}
+query = SELECT 'smtp:[${SMTP_RELAY_HOST}]:${SMTP_RELAY_PORT}' FROM relay_domain WHERE domain='%s'

images/postfix-pgsql/tests/setup.md

@@ -0,0 +1,142 @@
+# Local Test Environment Setup
+
+Step-by-step instructions for standing up a self-contained test environment for
+the `postfix-pgsql` image on any Linux host with Docker installed. No cloud
+access is required.
+
+## Architecture
+
+```
+External SMTP client (e.g. swaks / telnet)
+        |
+        | :25
+        v
+  [ postfix-pgsql ]  ──pgsql lookup──>  [ postgres ]
+        |
+        | :2525 (SMTP_RELAY_PORT)
+        v
+    [ mailhog ]   <── captured mail browsable at :8025
+```
+
+MailHog acts as a stand-in for the downstream SMTP consumer and captures every
+message delivered to it, making it easy to verify end-to-end relay without
+actually sending real mail.
+
+## 1. Create a dedicated Docker network
+
+All containers must share the same network so they can resolve each other by
+container name (required because chroot is disabled in this image — see the
+README).
+
+```bash
+docker network create postfix-test-net
+```
+
+## 2. Start PostgreSQL with the relay_domain schema
+
+```bash
+docker run -d \
+  --name test-postgres \
+  --network postfix-test-net \
+  -e POSTGRES_USER=relayuser \
+  -e POSTGRES_PASSWORD=testpassword \
+  -e POSTGRES_DB=relaydb \
+  postgres:16-alpine
+```
+
+Wait for Postgres to be ready, then create the `relay_domain` table and insert
+a test domain:
+
+```bash
+docker exec -i test-postgres psql -U relayuser -d relaydb <<'SQL'
+CREATE TABLE relay_domain (domain TEXT PRIMARY KEY);
+INSERT INTO relay_domain VALUES ('example.com');
+SQL
+```
+
+Verify:
+```bash
+docker exec -i test-postgres psql -U relayuser -d relaydb -c "SELECT * FROM relay_domain;"
+```
+
+## 3. Start MailHog
+
+MailHog listens on port 2525 for SMTP (matching `SMTP_RELAY_PORT`) and exposes
+a web UI on port 8025.
+
+```bash
+docker run -d \
+  --name test-mailhog \
+  --network postfix-test-net \
+  -p 8025:8025 \
+  mailhog/mailhog \
+  MailHog -smtp-bind-addr 0.0.0.0:2525
+```
+
+## 4. Start the postfix-pgsql container
+
+```bash
+docker run -d \
+  --name test-postfix \
+  --network postfix-test-net \
+  -p 25:25 \
+  -e MAIL_DOMAIN=example.com \
+  -e MYHOSTNAME=mx1.example.com \
+  -e POSTGRES_HOST=test-postgres \
+  -e POSTGRES_PORT=5432 \
+  -e POSTGRES_USER=relayuser \
+  -e POSTGRES_PASSWORD=testpassword \
+  -e POSTGRES_DB=relaydb \
+  -e SMTP_RELAY_HOST=test-mailhog \
+  -e SMTP_RELAY_PORT=2525 \
+  gitea.arnodo.fr/damien/postfix-pgsql:latest
+```
+
+Confirm it started cleanly:
+```bash
+docker logs test-postfix
+```
+
+Expected: Postfix master process line and no errors.
+
+## 5. Send a test message
+
+You can use `swaks` (Swiss Army Knife for SMTP) or plain `telnet`:
+
+```bash
+# With swaks (install: apt install swaks / brew install swaks)
+swaks --to user@example.com \
+      --from sender@external.com \
+      --server 127.0.0.1 \
+      --port 25
+
+# Or with telnet
+telnet 127.0.0.1 25
+  EHLO test
+  MAIL FROM:<sender@external.com>
+  RCPT TO:<user@example.com>
+  DATA
+  Subject: Test
+  .
+  QUIT
+```
+
+## 6. View captured mail in MailHog
+
+**Web UI** — if testing on a remote host, open an SSH tunnel first:
+```bash
+ssh -L 8025:localhost:8025 user@your-host
+```
+Then open `http://localhost:8025` in a browser.
+
+**HTTP API** (no tunnel needed):
+```bash
+curl -s http://localhost:8025/api/v2/messages | jq '.items[].Content.Headers.Subject'
+```
+
+## 7. Cleanup
+
+```bash
+docker rm -f test-postfix test-mailhog test-postgres
+docker network rm postfix-test-net
+```

images/postfix-pgsql/tests/test-plan.md

@@ -0,0 +1,23 @@
+# Test Plan: postfix-pgsql image
+
+Manual test suite run against the image during initial validation on a Scaleway
+test VM. All tests use the local environment described in `setup.md`.
+
+**Convention for this table:**
+- *Command(s)* are abbreviated; see `setup.md` for full environment setup.
+- Add new rows at the bottom as the image evolves; do not rewrite existing rows
+  (failed + fixed tests are part of the history).
+- Status: ✅ Pass · ❌ Fail · 🔧 Fixed (failed, root-caused, fix applied)
+
+| # | Test | What was checked | Command(s) | Expected | Actual | Status |
+|---|------|-----------------|------------|----------|--------|--------|
+| 1 | Clean startup | No errors in container logs after start; Postfix master process running | `docker run ... gitea.arnodo.fr/damien/postfix-pgsql:latest` then `docker logs test-postfix` | Postfix `daemon started` line, no `fatal`/`panic` entries | Logs show `postfix/master[1]: daemon started -- version 3.7.x`, self-signed cert generation output, no errors | ✅ Pass |
+| 2 | Missing required env var | Container exits with a clear error message when a required variable is absent | `docker run ... -e POSTGRES_HOST= ...` (POSTGRES_HOST set to empty) | Non-zero exit, `ERROR: required environment variable POSTGRES_HOST is not set` printed to stderr | Container exited immediately with the expected message | ✅ Pass |
+| 3 | Template rendering correctness | Rendered `main.cf` contains substituted values, no leftover `${VAR}` placeholders | `docker exec test-postfix cat /etc/postfix/main.cf` | `myhostname = mx1.example.com`, `mydomain = example.com`, TLS paths resolved, no literal `${...}` strings | All values substituted; Postfix-native `$mydomain` references (no braces) correctly left untouched by envsubst | ✅ Pass |
+| 4 | Self-signed TLS cert auto-generated | When no TLS_CERT_FILE/TLS_KEY_FILE are provided, a self-signed cert is generated and persisted | Start container without TLS vars; `docker exec test-postfix ls -l /etc/postfix/ssl/` | Files `snakeoil.pem` and `snakeoil.key` present; key mode 600 | Both files created on first start; `postconf smtpd_tls_cert_file` returned the correct path | ✅ Pass |
+| 5 | Port 25 reachable | SMTP port 25 is accessible from outside the container and returns a valid Postfix banner | `telnet 127.0.0.1 25` | `220 mx1.example.com ESMTP Postfix` banner | Banner received as expected | ✅ Pass |
+| 6 | Accepted domain → mail relayed | Mail sent to a recipient whose domain is in `relay_domain` is forwarded to the downstream SMTP target (MailHog) | `swaks --to user@example.com --server 127.0.0.1 --port 25`; check MailHog API | `250 2.0.0 Ok: queued` from Postfix; message appears in `GET /api/v2/messages` | Message delivered to MailHog and visible in the web UI | ✅ Pass |
+| 7 | Unknown domain → relay denied | Mail sent to a domain not in `relay_domain` is rejected with relay access denied | `swaks --to user@notlisted.org --server 127.0.0.1 --port 25` | `554 5.7.1 Relay access denied` | Postfix returned `554 5.7.1 <user@notlisted.org>: Relay access denied` | ✅ Pass |
+| 8 | PostgreSQL lookup failure — chroot DNS bug | pgsql-backed `relay_domains`/`transport_maps` lookups work correctly when Postgres is referenced by Docker container name | Send mail to `user@example.com` with `POSTGRES_HOST=test-postgres` (container name, not IP) | `250 Ok: queued`; no `451 Temporary lookup failure` in logs | **Without fix:** intermittent `451 4.3.0 Temporary lookup failure` — chrooted child processes (smtpd, trivial-rewrite) could not resolve `test-postgres` because they lack `/etc/resolv.conf` inside the chroot jail. **Fix applied:** added `postconf -F '*/*/chroot = n'` in `docker-entrypoint.sh` before `postfix start-fg`. After fix: lookups succeed consistently. | 🔧 Fixed |
+| 9 | Container restart behavior | Config is re-rendered correctly on restart; pre-existing self-signed cert is reused without re-generation | `docker restart test-postfix`; `docker logs test-postfix` | No re-generation message for TLS cert; `main.cf` and pgsql maps fully substituted; Postfix starts without errors | Cert reuse message absent (new cert would log openssl output); Postfix started cleanly on restart | ✅ Pass |
+| 10 | No credential leakage in logs | Postgres password does not appear anywhere in `docker logs` output | `docker logs test-postfix 2>&1 \| grep testpassword` | No output (password not printed) | No lines containing the password; envsubst substitution into config files is silent | ✅ Pass |