lukasandClaude Opus 5
f3dcd938b1
DSM reported "invalid interpolation format for x-backend-env.MASTER_KEY" and
"required variable MASTER_KEY is missing a value". Both were mine.
1. DSM's bundled Compose cannot parse `${VAR:?message}`. Those guards are gone;
interpolation now sticks to `${VAR}` and `${VAR:-default}`, the forms every
Compose understands. Bind mounts keep a `${DATA_ROOT:-/DATA_ROOT-is-unset}`
sentinel so a missing config still cannot scatter directories across the
root of the NAS filesystem, and the header says to keep it this way.
2. Config was at docker/.env.prod with a `.env` symlink beside it. Container
Manager did not pick that up. The real file is now `.env` in the project
folder — what every compose front end reads without being told — and
docker/.env.prod becomes a symlink to it. `init` and `require_env` migrate
an existing install in place, keeping its MASTER_KEY.
Also, while testing the migration: `init` only generated secrets when creating
a file from scratch, so a migrated or hand-written .env with an empty
POSTGRES_PASSWORD started Postgres in trust-auth mode. It now tops up empty
secrets — and never touches a MASTER_KEY that already has a value, since
replacing it would make every stored credential undecryptable. doctor flags an
empty password too.
Verified: parses cleanly with no .env at all (the failure DSM hit), migration
preserves an existing key, and `docker compose up -d --wait` from the project
folder brings the stack up healthy and serving.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nux3LCu4zP9nih4BRhPyHw
17 KiB
Running Webmail on a Synology or QNAP NAS
This is the operator runbook: how to install it, how to keep your mail safe from anything Docker does to itself, and how to update without holding your breath. It assumes the NAS is doing other work too, so the stack is deliberately modest: one published port, no host networking, memory caps on every container.
Everything here works on any Intel/AMD Docker host — the NAS parts are just the specifics for DSM and QTS.
1. What gets installed
| Container | What it does | Published? |
|---|---|---|
web |
nginx: serves the UI, proxies /api (incl. the WebSocket) |
yes — the only one |
api |
FastAPI app | no, internal network only |
worker-sync |
keeps IMAP connections open, syncs mail | no |
worker-jobs |
background jobs (send, backfill, purge, plugin jobs) | no |
postgres |
the database | no |
redis |
job queues + sync leases | no |
backup |
nightly verified database dump | no |
meilisearch |
optional better search (see §8) | no |
migrate, init |
run once at start, then exit | — |
Plugins (calendar, contacts, labels, filters) are baked into the backend image and their database schema is applied automatically on every start.
Requirements: an Intel/AMD NAS with Docker (Synology Container Manager, QNAP Container Station), ~2 GB RAM free, and 10 GB+ of disk for a typical personal mailbox. Nothing is needed from the internet except your mail servers.
2. Install
2.1 Pick where the data lives
This is the single most important decision. Use a shared folder, never a Docker named volume:
| NAS | Use |
|---|---|
| Synology | /volume1/docker/webmail/data |
| QNAP | /share/Container/webmail/data |
Why: named volumes live inside Docker's internal storage, where Hyper Backup, Snapshot Replication and HBS3 cannot see them, and where "delete the project" in the NAS UI can take your mail with it. A shared folder is backed up by the tools you already run, survives every container operation, and can be copied to another machine wholesale.
Never put this on an NFS or SMB mount. Postgres on a network filesystem corrupts.
./deploy/webmail.sh doctorchecks this and refuses to be quiet about it.
2.2 Get the code onto the NAS
Enable SSH on the NAS (DSM: Control Panel → Terminal & SNMP → Enable SSH; QTS: Control Panel → Telnet/SSH), then:
ssh admin@your-nas
sudo -i
mkdir -p /volume1/docker/webmail && cd /volume1/docker/webmail
git clone <your-gitea-url>/webmail.git src && cd src
No git on the NAS? Copy the folder over with File Station or rsync instead.
2.3 Configure
./deploy/webmail.sh init
This creates .env with a freshly generated MASTER_KEY and
database password. Then open it and set:
DATA_ROOT=/volume1/docker/webmail/data # or /share/Container/webmail/data
APP_DOMAIN=mail.home.lan # your handles become you@this
TZ=Europe/Warsaw
WEB_PORT=8088 # avoid 5000/5001 (DSM), 8080 (QTS)
WEB_BIND=0.0.0.0 # or one NAS IP, e.g. 192.168.1.185
Copy
MASTER_KEYinto your password manager. Now.It encrypts every stored mail-account password. It exists only in this file. A perfect database backup without this key gives you your mail but not your credentials — you would have to re-enter every account password by hand.
.envischmod 600and git-ignored; treat it as a backup artefact in its own right.
2.4 Start
./deploy/webmail.sh doctor # sanity-checks config, disk, filesystem, ports
./deploy/webmail.sh up # builds the images on first run, then starts
First run builds both images. The frontend build wants ~2 GB of RAM: if your NAS is small or you'd rather not tie it up, build on your PC instead — see §6.3.
Open http://your-nas:8088/, create your account, and add a mail account
through the wizard.
2.5 Installing entirely from the DSM GUI (no SSH)
The whole install can be done without ever enabling SSH. The trick is Task Scheduler: it runs any shell command as root from the DSM web UI, which covers the three things the Container Manager UI cannot do on its own.
1. Get the code onto the NAS. In Gitea, open the repository and use
Download ZIP (the <> Code button). In DSM, open File Station, create
docker/webmail/, upload the zip into it, then right-click → Extract here.
Rename the extracted folder to src, so you end up with
/volume1/docker/webmail/src/docker-compose.yml.
2. Configure it — one Task Scheduler job. Control Panel → Task Scheduler → Create → Scheduled Task → User-defined script. Set User: root, leave it unscheduled, and paste this as the script (adjust the four values):
cd /volume1/docker/webmail/src
chmod +x deploy/*.sh docker/*.sh
bash deploy/webmail.sh init \
--data-root /volume1/docker/webmail/data \
--domain mail.home.lan \
--tz Europe/Warsaw \
--port 8088
Save, select the task, and click Run. The chmod line matters: a zip download
loses the executable bit. This generates MASTER_KEY, a database password, and
the .env that Container Manager will read — with no hidden files to edit.
3. Back up the master key — a second one-off task. Same recipe, script:
cd /volume1/docker/webmail/src
bash deploy/webmail.sh show-key > /volume1/docker/webmail/MASTER_KEY.txt
Run it, open MASTER_KEY.txt in File Station, copy the key into your password
manager, then delete the file.
Doing this from an SSH shell instead?
initcreated that file as root with mode 600, so run it as root or you get "Permission denied":sudo bash deploy/webmail.sh show-key. The same goes for every other command here — the data directories are root-owned, so start withsudo -i. Skipping this is the one mistake with no recovery: without that key, no backup can decrypt your saved mail-account passwords.
4. Create the project. Container Manager → Project → Create:
| Field | Value |
|---|---|
| Project name | webmail-prod |
| Path | /volume1/docker/webmail/src |
| Source | it will find docker-compose.yml — choose to use the existing file |
Pick the repo root, not docker/. Both contain a docker-compose.yml, and
the one in docker/ is the throwaway dev service stack — starting it gives
you containers but no webmail server. Use the project name webmail-prod
exactly: the name typed here overrides the one in the file, and matching them
means the GUI and deploy/webmail.sh drive the same stack.
Click through, and it builds. First build takes 5-15 minutes and wants ~2 GB of RAM — it compiles the frontend on the NAS. This is the one place the GUI route is meaningfully worse than SSH, where you can build on your PC and copy the images over (§6.3).
5. Open http://your-nas:8088/ and register your account.
What you will see in Container Manager: init and migrate sitting at
Exited (0). That is correct — they are one-shot jobs that did their work and
stopped, and everything else waited on them.
Running the maintenance commands without a shell
Task Scheduler is not just for setup — it runs any of these, and can schedule
them. Each is a user-defined script, user root, starting with
cd /volume1/docker/webmail/src:
| Task | Script line | When |
|---|---|---|
| Update safely | bash deploy/webmail.sh update |
after pulling new code |
| Roll back | bash deploy/webmail.sh rollback |
if an update misbehaves |
| Backup now | bash deploy/webmail.sh backup |
before anything risky |
| Restore | echo RESTORE | bash deploy/webmail.sh restore <file> |
disaster recovery |
| Health check | bash deploy/webmail.sh doctor |
when something looks wrong |
| Rebuild search | bash deploy/webmail.sh reindex --purge |
after a restore |
Updating through the Container Manager UI instead (project → Build) does work
and does apply migrations — but it takes no backup first, has no health gate,
and will not roll back if the new version fails to start. The update task
above does all three. Use it.
2.6 Starting automatically after a reboot
Every service is restart: unless-stopped, so Docker brings the stack back on
boot by itself. On Synology, make sure Container Manager itself is set to start
on boot (it is by default).
3. The three things that matter
Containers are disposable. These are not:
| # | What | Where | If you lose it |
|---|---|---|---|
| 1 | Database | $DATA_ROOT/postgres + nightly dumps in $DATA_ROOT/backups |
Everything: accounts, threads, flags, calendar, contacts |
| 2 | Blob store | $DATA_ROOT/blobs |
Mail bodies and attachments (re-downloadable from the servers, slowly) |
| 3 | MASTER_KEY |
.env + your password manager |
Every saved mail-account password, permanently |
Everything else is derived and needs no backup: Redis holds queues and leases, Meilisearch's index rebuilds from Postgres (§8), and images rebuild from source.
Backups
Two layers, and you want both:
Nightly dumps (automatic). The backup container writes a compressed
pg_dump to $DATA_ROOT/backups at BACKUP_AT (default 03:30) and keeps
BACKUP_KEEP_DAYS (14) of them. Every dump is verified with pg_restore --list
before it counts, so you never find out at restore time that it was truncated.
Off-box copies (you set this up, once). Point your NAS backup tool at
$DATA_ROOT:
- Synology: Hyper Backup → local/remote/cloud destination → include the
docker/webmailshared folder. Add Snapshot Replication on a Btrfs volume for fast local rollback. - QNAP: HBS 3 → the
Container/webmailfolder. Add snapshots on QuTS hero.
A snapshot of a running Postgres directory is crash-consistent — it usually replays fine, but it is not a substitute for the dumps, which are verified and restorable into a different Postgres version. Keep both.
Also back up .env somewhere that is not the NAS.
Restore drill — do this once, before you need it
./deploy/webmail.sh status # see available dumps
./deploy/webmail.sh restore webmail-20260914-033000.dump
It stops the app containers, restores in a single transaction (a failure leaves the old database untouched), and starts everything back up.
Full disaster recovery onto a new box:
- Install Docker, copy
$DATA_ROOTback from your backup. - Copy the repo and
.env— with the originalMASTER_KEY. ./deploy/webmail.sh up
That's it. If the blob store was lost but the database survived, mail bodies refill from the mail servers as accounts re-sync.
4. Updating
git pull
./deploy/webmail.sh update
update does, in this order, stopping the moment anything fails:
- Takes a verified database backup. No backup, no update.
- Builds (or pulls) the new images. A failure here changes nothing.
- Runs migrations as a one-shot container — before any service restarts, so a bad migration never leaves new code running against an old schema.
- Rolls workers first, then API, then web. Sync leases transfer to the replacement worker within ~90 s and message upserts are idempotent, so no mail is lost or duplicated by a roll.
- Health-gates for 120 s. If the new version doesn't come up healthy it rolls itself back automatically and leaves you on the previous version.
To go back manually:
./deploy/webmail.sh rollback # previous version
./deploy/webmail.sh rollback v1.2.0 # a specific one
Rolling code back does not require rolling the schema back, as long as
migrations stay expand-then-contract (see docs/migrations.md discipline in
deployment-setup-instructions.md §9). For the rare breaking migration, restore
the dump that update took in step 1.
Building images elsewhere
Building on the NAS is simple but slow and RAM-hungry. Two alternatives:
# On your PC — push to your Gitea registry:
REGISTRY_PREFIX=192.168.1.185:8418/claude/webmail ./deploy/build-push.sh v1.0.0
# then on the NAS, set REGISTRY_PREFIX + IMAGE_TAG in .env and:
./deploy/webmail.sh update v1.0.0
# Or with no registry at all — build to a file and carry it over:
./deploy/build-push.sh v1.0.0 --save
# copy webmail-v1.0.0.tar to the NAS, then:
docker load -i webmail-v1.0.0.tar && ./deploy/webmail.sh update v1.0.0
5. Reaching it from outside the LAN
5.1 Read this first
Anyone who can open the page can create an account on it. Registration is open by design (it's a personal server), so do not put this straight on the public internet. Pick one:
- VPN (Tailscale, WireGuard, or the NAS's own VPN Server) — simplest and safest. The port stays LAN-only.
- NAS reverse proxy with HTTPS, restricted by firewall rules to the networks you trust.
5.2 HTTPS through the NAS reverse proxy
DSM owns ports 80/443, which is why the stack publishes 8088. To put DSM's certificate in front of it:
Control Panel → Login Portal → Advanced → Reverse Proxy → Create
| Field | Value |
|---|---|
| Source protocol / hostname / port | HTTPS / mail.yourdomain / 443 |
| Destination protocol / hostname / port | HTTP / localhost / 8088 |
Then open Custom Header → Create → WebSocket and save. Without that,
/api/ws is blocked and the UI stops updating live.
QNAP: Network & Virtual Switch → Reverse Proxy — same idea, and likewise enable WebSocket support.
Session cookies get the Secure and __Host- treatment automatically as soon
as the app sees an HTTPS request: nginx forwards X-Forwarded-Proto, and the
API is started with --proxy-headers. Nothing to configure.
6. Resource usage
Steady state for one or two mail accounts, SEARCH_BACKEND=pg:
| Typical | Cap (.env) |
|
|---|---|---|
| postgres | 150-300 MB | PG_MEM_LIMIT=768m |
| api | 150-250 MB | API_MEM_LIMIT=512m |
| worker-sync | 120-250 MB | WORKER_SYNC_MEM_LIMIT=512m |
| worker-jobs | 150-350 MB | WORKER_JOBS_MEM_LIMIT=640m |
| redis / web / backup | < 100 MB total | — |
| total | ~0.7-1.2 GB | ~2.2 GB of limits |
| meilisearch (optional) | 300-800 MB | MEILI_MEM_LIMIT=1g |
On a 2 GB NAS: stay on SEARCH_BACKEND=pg and drop PG_SHARED_BUFFERS to
128MB. Tight but workable. On 4 GB+ you have room for Meilisearch.
Two NAS-specific realities worth knowing:
- Disk hibernation won't happen. Active accounts hold IMAP IDLE connections open and write as mail arrives. That is the feature working, not a bug.
- Keep NTP on. Two-factor codes fail on a drifting clock.
7. Search: Postgres or Meilisearch
SEARCH_BACKEND=pg (default) uses Postgres full-text search. No extra
container, no extra RAM, and it is perfectly good for a personal mailbox.
SEARCH_BACKEND=meili adds typo tolerance, better ranking and stays fast on
large mailboxes, at the cost of a container and 300-800 MB.
To switch:
# in .env: SEARCH_BACKEND=meili and set MEILI_MASTER_KEY
./deploy/webmail.sh up # starts Meilisearch automatically
./deploy/webmail.sh reindex # build the index from existing mail
The index is derived data — every field it holds also lives in Postgres — so it never needs backing up. If the Meilisearch volume is lost, or you switch backends, or search ever looks stale, just rebuild it:
./deploy/webmail.sh reindex # upsert everything (safe to re-run)
./deploy/webmail.sh reindex --purge # drop stale documents first
8. Troubleshooting
| Symptom | Cause | Fix |
|---|---|---|
up hangs on postgres |
DATA_ROOT on NFS/SMB, or wrong permissions |
./deploy/webmail.sh doctor |
| UI loads, no live updates | WebSocket not enabled in the NAS reverse proxy | §5.2 Custom Header → WebSocket |
| Login works, logs out on reload | HTTPS terminated upstream but X-Forwarded-Proto stripped |
Use the NAS reverse proxy as documented; don't strip headers |
| "port is already allocated" | 8088 taken by another app | change WEB_PORT |
| Mail not syncing | worker stopped, or credentials rejected | ./deploy/webmail.sh logs worker-sync |
| Search finds nothing after a restore | index not rebuilt | ./deploy/webmail.sh reindex --purge |
App won't start after editing .env |
malformed MASTER_KEY |
./deploy/webmail.sh doctor |
Logs: ./deploy/webmail.sh logs [service] -f. All logs are capped at 10 MB ×3
per container, so they can't fill the volume.
9. Command reference
Run these as root (sudo -i first): the env file is mode 600 and the data
directories are root-owned.
./deploy/webmail.sh init [flags] create data dirs + generate secrets
./deploy/webmail.sh show-key print MASTER_KEY so you can back it up
./deploy/webmail.sh doctor pre-flight checks
./deploy/webmail.sh up [--meili] start everything
./deploy/webmail.sh down stop (data untouched)
./deploy/webmail.sh status what's running, versions, disk, backups
./deploy/webmail.sh logs [svc] [-f] logs
./deploy/webmail.sh update [tag] backup -> migrate -> roll -> health-gate
./deploy/webmail.sh rollback [tag] back to the previous version
./deploy/webmail.sh backup verified dump, right now
./deploy/webmail.sh restore <dump> restore a dump (asks for confirmation)
./deploy/webmail.sh reindex [--purge] rebuild the search index
./deploy/webmail.sh psql database shell
./deploy/webmail.sh shell [svc] shell in a container