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README.md

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+# README.md — Docker Mailserver (DMS) Setup for knusperkerne.de
+
+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.