This document describes the stable, minimal configuration of your Docker Mailserver (DMS) installation and the daily operational commands required to manage domains and users.

1. Project Structure

The directory contains:

compose.yml
.env
config/postfix-main.cf
config/postfix-master.cf
config/postfix-accounts.cf
config/postfix-virtual.cf
config/opendkim/*
volumes: maildata, mailstate, maillogs
snappymail/ (webmail)

2. Services

mail (Docker Mailserver 12.x)

Hostname: mailsystem.knusperkerne.de
Ports: SMTP(25), SUBMISSION(587), IMAPS(993)
Configuration directory mounted to /tmp/docker-mailserver
SPF-Checks fully disabled via postfix-main.cf and postfix-master.cf overrides
DKIM enabled via /config/opendkim

snappymail (Webmail)

Bound to 127.0.0.1:${SNAPPYMAIL_PORT}
Stores data in ./snappymail

3. Essential Admin Commands

All commands are executed inside the mailserver container:

Enter the container

docker exec -it mailserver bash

3.1 Add a domain

Domains do not require a separate explicit create-command.
To ensure DMS recognizes a domain, add a dummy account: setup email add dms-domain-init@yourdomain.de somepassword

After DNS MX + A records propagate, the domain becomes active.

3.2 Add a real user

setup email add USER@DOMAIN.TLD PASSWORD

3.3 Change a user password

setup email update USER@DOMAIN.TLD PASSWORD

3.4 Delete a user

setup email del USER@DOMAIN.TLD

3.5 List all accounts

setup email list

3.6 Show mailbox sizes

du -sh /var/mail/vhosts/DOMAIN.TLD/USER/

3.7 Rebuild postfix/dovecot after config changes

Supervised automatically at startup; restart the container after modifying any file under config/: docker compose restart mail

4. Config Overrides

4.1 postfix-main.cf

Disables SPF policy checks completely
Keeps only minimal safe recipient checks:

policyd-spf_time_limit = 0 smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination

4.2 postfix-master.cf

Overrides the policyd-spf service to discard:

policyd-spf unix - n n - 0 discard

4.3 postfix-accounts.cf

Auto-generated by DMS. Contains user → password-hash entries.

4.4 postfix-virtual.cf

Virtual alias configuration for mail routing.

5. DNS Requirements

For each domain:

MX 10 mailsystem.knusperkerne.de
A mailsystem.knusperkerne.de → YOUR.SERVER.IP
SPF TXT (liberal): "v=spf1 a mx ~all"
DKIM: Add the public key from config/opendkim/keys/DOMAIN/mail.txt

6. Backup

Backup volumes: maildata, mailstate
Backup config/: postfix configs and DKIM keys
Logs are in maillogs/

7. Notes

SPF checks are intentionally disabled (forwarding-friendly).
DKIM signing remains active and reliable for reputation.
DMS v12 receives security updates and remains stable.
No additional MTA/MDA components are required; Postfix+Dovecot are fully integrated.