mixandClaude Opus 5.5
af130e268a
Technical review (Opus) and security review (Fable) of 5be109b..5154bba;
reports in the session's scratchpad. Nothing above low from security; one
bug and three risks from the technical review. Migration 0009 is not
deployed, so it was extended.
- Bug: two refusals of one second swapped their NOQUEUE lines (each line
went to the newest lineless row). AttachRefusalLine now matches the
client address too (send_log.client_ip, written by the journal milter -
Postfix's line names the client and the sender, never the login: the
sasl_username part of the pattern never matched and could be fed by HELO,
security F1/F2), takes the nearest row in time and the oldest of equals,
and a line already on a row goes on no other (security F6).
- Waiting lines and recoveries lived only in memory while the saved offset
moved past them: a stop within 30 s lost them. The tracker now never saves
an offset past the oldest waiting item in its file (tracker.hold,
refusalLines.oldest) - for a recovery, the client= line that names its
login - so they are read again; the "once" guards make that harmless.
- A recovered row whose login the tailer did not see was nobody's: its
domain_id falls back to the envelope domain's.
- The fingerprint's file identity is the inode alone: the device number can
change across a host reboot and make the same log look rotated.
- A refused row carries its queue id; UpdateStatus's "newest row" now skips
refused rows, so a later message with that id does not flip it to sent.
- The alive mark: its age is read first and kept from then on, so asking
supervisord for 30 s cannot make it stale; the entrypoint removes it with
the sockets - a container restart is not the check's downtime, and a mark
from before would have counted the whole outage as "≈".
- Security F3: the sender check prints no ";" of the client's in the From:
text of its reply, and the tailer reads the envelope after the first ";"
- Postfix's own text.
- A refused row with a queue id and no stored lines says so (it was told the
mail.log text of 2.2.0); the fact's em dash is the house hyphen.
- Docs: architecture (client address, no login), guide § Health (warns on
either count), help topics log and sender-check (design 1ca87f2).
- e2e: refusals_show_postfixs_line wants the refusal's own sender in the
line; refusal_recovered_from_the_log waits past the tailer's 30 s and
checks that a refusal the panel wrote got no recovered twin.
Not changed, written down: review 9 (mail.log.1 read to its end at that
moment; postlogd may still write to it until the reload), 10 (a log under
512 bytes has no fingerprint, so places fall back to time briefly after a
rotation), 6 (a 451 at MAIL FROM of another milter reads the same - the
client and sender must match too now), security F5/F12 (info). Review 12:
the refused and closed-by-the-panel variants of out-message were shown to
the owner as pictures of the real templates, not drawn in out-message.html:
the guard ties every drawn screen to a page of the engine, and a variant
has the page's outline.
Evidence on the test server for this tree: go vet clean, go test ./... 23
packages ok, make e2e exit 0 (refusal_recovered_from_the_log 70 s).
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=2.5.0 \ -t ghcr.io/mixeme/selfpost:2.5.0 .
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:2.5.0
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.