mixandClaude Opus 5.5
cad1182150
All 2026-10-15; each written beside the code or text it settles. - A-43: /usr/sbin/postlog is -rwxr-xr-x root:root in the image (postfix 3.7.11-0+deb12u1; dpkg-statoverride lists postdrop and postqueue only): Debian does not install it set-gid, so it is no use to dmarc-ingest (cmd/panel/dmarc_ingest.go). - C-X1: OpenSSL 3.0.22 in the image prints the same public key from `x509 -pubkey` and `pkey -pubout` for RSA-2048, P-256, P-384 and a SEC1 P-256 key - cert-reload's same_pair holds for certbot's ECDSA keys. - C-K5, D-guide:933/:233: on the live server (Docker 29.6.1, userland proxy on 0.0.0.0 and ::, no IPv6 on the network) an outside IPv4 client and the host's own public IPv4 address are logged as themselves; the host's IPv6 address and 127.0.0.1 arrive as 172.18.0.1. Over IPv6 every client is the gateway: one level-1 budget, an application IP list cannot name them, rspamd sees the gateway. Guide paragraph under level 1, notes at the milter and allow-list, comments at the anvil setup and authip.go, and a Security entry in the CHANGELOG (an allow-list naming the gateway would admit every IPv6 client). - D-guide:61: a published port nothing listens on (a throwaway container, -p 20999:25) is refused from outside over IPv4 and from the host's public IPv4, accepted and closed through 127.0.0.1 - Docker's proxy, which IPv6 goes through too (not probed over IPv6 for this). - C-M8: the live installation has received one DMARC report, of one record: nothing to set maxReportRecords by yet - said at the constant. - D-S7, D-arch:516, D-arch:532: a new database filled through the store to 120 days at 1 900 messages a day (228 000 messages, 1.37 million lines, 464 MB) on the test server (2 cores): the longest write is the line prune after a 30-day gap, 1.9 s for 342 000 lines (0.4 s with nothing to delete); the send-log delete 0.6 s; 2 000 lines of a tailer pass 18 ms; VACUUM INTO 1.7 s; a second connection writing every 50 ms waited 1.8 s at most, no SQLITE_BUSY - inside busy_timeout's 5 s. architecture.md's "about a second per million lines" was five times too fast; its "six to ten lines of 200 bytes" is 6.0 lines of 146 bytes on the live data. - D-B16: which favicon is fetched, by the probe server's log: Edge 155 the SVG, the desktop app's embedded Chromium 152 the PNG, with or without sizes="any" - layout.html's "vector wins where supported, raster catches the rest" holds; Firefox and Safari not measured. - D-arch:121: the allow/deny trial again, in rspamd/rspamd:3.11.1-3 with today's multimap.conf: every mix of allow and deny entries matching one message ended reject; a changed map was used about 10 s later. - D-sec:424: rspamd runs as _rspamd, uid 11333; the panel is uid 999. Stand: go vet and go test ./... pass on the server (24 packages); make e2e exit 0. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
SelfPost
Self-hosted SMTP relay with a web panel — one Docker image, no provider.
Postfix, OpenDKIM, and a small Go panel run together under supervisord; you
configure domains, DKIM keys, and SASL applications once, then point your apps
at the SMTP endpoint.
SelfPost sends mail straight to the internet from your own IP, with per-domain DKIM signing. No mailboxes or webmail. An optional inbound relay (backup-MX / forwarder on port 25) forwards to an upstream; it does not store mail.
For: operators who run their own VPS or home server and want a simple relay they control, without a third-party SMTP provider.
Key properties: one container, multi-domain DKIM, SASL per application, send log and DNS checks in the panel, encrypted backups.
Features
- Outbound SMTP (465/smtps; optional 587 submission) with per-domain DKIM signing
- Optional inbound relay on port 25 (backup-MX / forwarder; off by default)
- Optional DMARC aggregate report ingest on port 25 (off by default)
- In-panel Help: a page of topics, opened from the
?in the head of a box - Per-application client IP allow-list for SMTP AUTH (optional)
- Web panel grouped by mail direction — Overview, Outbound (domains, log, queue, DMARC reports), Inbound, Server (health, system log, backup, users, settings)
- Multi-domain relay — each SASL application is bound to one sending domain
- DNS status checks (PTR, SPF, DKIM, DMARC) with in-panel re-check
- Two-level rate limiting — IP backstop (Postfix), per-domain ceilings, and trusted-IP app overrides
- Full-server backup and single-domain export/import (optional password encryption)
- Single Docker image; production data in a
./databind mount (the quick start below uses a named Docker volume instead)
Documentation
| Document | Contents |
|---|---|
| Operator guide | Reverse proxy, environment variables, DNS, IP warmup, panel operations, rate limiting, backup/restore, ports, image tag |
| Product boundaries | Purpose, deployment assumptions, out-of-scope items, multi-domain model |
| Architecture | As-built technical design |
| Security design | Mandatory requirements, accepted risks, the CSRF ADR |
| Development | Building, testing, docs rules, model routing, commits |
| Roadmap | Open work (1.x+) — direction, not commitments |
| CHANGELOG | Release history |
Found a vulnerability? Do not open an issue — SECURITY.md has the private reporting channel and the scope.
Repository: https://github.com/mixeme/selfpost — source, issues, releases, and
the ghcr.io/mixeme/selfpost image.
Requirements
Providing these is the operator's job — SelfPost cannot fix a blocked port or a missing PTR record for you. Details: Operator guide.
Platform
- Docker + Compose v2 on the host
- A reverse proxy in front of the panel (SelfPost never terminates HTTPS itself)
- Rough sizing: 1 vCPU, 512 MB–1 GB RAM, 8–10 GB disk (send log and
rotated
mail.logare the main growth drivers; both sit in the./datavolume, and both are capped — 90 days and 14 files by default)
Network and IP
- Static IP address
- Outbound TCP port 25 unblocked (many consumer/cloud hosts block it by default)
- PTR/rDNS for that IP pointing at your mail hostname (
SELFPOST_HOSTNAME) - Reasonable starting IP reputation — a fresh IP still needs warmup
Per sending domain
For every domain you add in the panel:
- SPF TXT record authorizing this server
- DKIM TXT record (value shown on the domain page)
- DMARC
_dmarcTXT record
See Domain-level DNS in the operator guide.
Per inbound domain (optional)
Only if you turn on inbound relay (INBOUND_RELAY_ENABLE=true):
- MX record pointing at
SELFPOST_HOSTNAME(keep any existing primary MX if this host is backup-MX)
See Inbound relay in the operator guide.
Quick start
First boot — create the admin account. On a fresh container SelfPost prints a one-time setup URL (valid ten minutes). Open it in a browser to choose the administrator username and password. Until you do, the panel has no login. Production deploy: Full deployment in the operator guide.
One container, panel at http://127.0.0.1:8080 — no reverse proxy, no TLS
files, no compose files. Good for clicking through the UI on your machine;
outbound mail will not reach the real internet without DNS, PTR, and port 25.
The 2.x line is not published on ghcr.io yet (the newest image there is
1.3.0). Until it is, build the image from this checkout under the name the commands below anddeploy/docker-compose.ymluse; Docker then takes the local image and pulls nothing:docker build -f build/Dockerfile --build-arg VERSION=2.5.1 \ -t ghcr.io/mixeme/selfpost:2.5.1 .
docker run --rm -d --name selfpost-try \
-p 127.0.0.1:8080:8080 \
-e SELFPOST_HOSTNAME=mail.local.test \
-e PANEL_COOKIE_SECURE=false \
-v selfpost-try-data:/data \
ghcr.io/mixeme/selfpost:2.5.1
Get the setup URL (pick one):
docker logs selfpost-try 2>&1 | grep -m1 'http'
docker exec selfpost-try cat /data/setup-token
The printed URL is https://mail.local.test/setup/<token>. For this local
trial rewrite it to http://127.0.0.1:8080/setup/<token> (same path token;
PANEL_COOKIE_SECURE=false so the cookie works over plain HTTP). Open it
before it expires.
When finished:
docker rm -f selfpost-try && docker volume rm selfpost-try-data
More detail (limitations, optional throwaway TLS for local SMTP): Local trial in the operator guide.
Reference deploy
Production layout: one docker-compose.yml, a .env, persistent ./data, and
TLS PEM files at ./certs (read by Postfix on 465/587). The panel is reached
only through a reverse proxy on 443 — port 8080 is bound to localhost in the
default compose file.
Full walkthrough — fetching the base files, setting up a reverse proxy and TLS (Apache/nginx/Caddy/Traefik), starting the container, and wiring up DNS — lives in the operator guide's Full deployment section, with proxy-specific commands under Reverse proxy.
The compose file always publishes 465, 587, and 25; Postfix listens
on 587 only when SUBMISSION_ENABLE=true, and on 25 when
INBOUND_RELAY_ENABLE=true and/or DMARC_REPORTS_ENABLE=true (see
Ports). Bump the
pinned image tag deliberately when upgrading, never :latest (why). Optional
variables (TRUSTED_PROXY_CIDR, rate limits, retention): see Environment
variables.
License
Copyright © 2026 Mikhail Yenuchenko.
AGPL-3.0. The AGPL closes the "SaaS loophole": if you run a modified version as a network-accessible service, you must make the modified source available to its users — not only when you distribute copies of the code. Third-party notices: NOTICE.