tailwart

Tailscale × Stalwart. A mailbox with no WAN presence, fronted by a layer-4 proxy that can live on another machine entirely.

A deliberately over-engineered playground: Stalwart mail server wired into Postgres + Redis + Garage S3 at once, deployed as a Tailscale sidecar, with a separate caddy-l4 edge that pipes the raw mail ports over the tailnet. For infinidim.net.

See CLAUDE.md for the architecture and the gotchas, and LESSONS.md for the hard-won symptom→cause→fix notes from bringing it up (PG races, ACME DNS-01, PROXY-protocol trust, IPv6 egress, …).

Layout

tailwart/
├── docker-compose.yml      # the mailbox: ts-stalwart sidecar + stalwart (+ IPv6 egress)
├── config/config.json      # Stalwart v0.16 bootstrap config — datastore (Postgres) ONLY
├── config/config.toml      # dead v0.15-era config, kept as historical reference
├── caddy/                  # the edge: custom Caddy (caddy-l4) layer-4 mail proxy
│   ├── Dockerfile          #   pulls prebuilt caddy-l4 binary (caddyserver.com, no local build)
│   ├── caddy.json          #   :25/465/587/143/993 mail + :443 SNI fan-out → stalwart over the tailnet
│   ├── docker-compose.yml  #   deploy on any public-IP, tailnet, tag:reverse-proxy host
│   └── README.md
├── acl-snippet.hujson      # tag:stalwart owner + grants to merge into your policy
├── .env.example            # operator surface — copy to .env
└── .gitignore

v0.16 config model: config.json describes only where Postgres lives; everything else (domains, accounts, listeners, ACME, blob/Redis wiring, proxy trust, DKIM, spam) lives in Postgres, managed via the web UI or JMAP. The old TOML + %{env}% macro model is gone — see CLAUDE.md / LESSONS.md.

Quickstart

cp .env.example .env && $EDITOR .env        # fill secrets (see CLAUDE.md prereqs)

# 1. create the stalwart role/db in shared Postgres + the Garage bucket
#    (one-off; see CLAUDE.md "Prerequisites")
# 2. admin console: assign tag:stalwart to the OAuth client + paste acl-snippet
# 3. bring up the mailbox (tailnet-only)
docker compose up -d
# 4. bring up the edge (binds public mail ports; can be a different host)
cd caddy && docker compose up -d --build

Then point infinidim.net's MX at the edge host, add SPF/DKIM/DMARC, and finish configuration in Stalwart's web admin (mail.infinidim.net).

Status

Live. Pinned to stalwartlabs/stalwart:v0.16.7, booting cleanly against the shared Postgres/Redis/Garage backends, holding a Let's Encrypt wildcard via ACME DNS-01 (Spaceship), and relaying outbound over the tailnet (the VPS blocks all outbound SMTP ports). The container has its own IPv6 egress.

Not yet exposed for inbound IPv6 mail: mail.infinidim.net is intentionally A-only until the edge proxy gains v6 :25 listeners — publish its AAAA and the v6 listeners together, or senders will try v6 and some won't fall back. See LESSONS.md.