added mailserver guide

docs/misc/linux/docker-mailserver.md

@@ -5,8 +5,127 @@ slug: /misc/linux/docker-mailserver
 
 # Docker Mailserver
 
-:::info
-// TODO:
-- install dockercompose
-- ...
-:::
+This guide installs docker-mailserver with SSL/TLS for secure incoming and outgoing mail. Below each step includes explanations of what it accomplishes.
+
+## Step 1: Create project directory
+```bash
+mkdir docker-mailserver
+cd docker-mailserver
+```
+
+## Step 2: Create SSL Certificates
+If your mail server domain is publicly accessible, use Certbot to obtain trusted SSL certificates for free.
+### use Let's Encrypt
+```bash
+sudo certbot certonly --manual --preferred-challenges dns -d mail.jonasjones.dev
+```
+Now, add a TXT DNS-Record as indicated by the instructions in the terminal, then hit enter.
+
+This creates certificates typically in /etc/letsencrypt/live/mail.example.com/:
+
+    - `fullchain.pem` — full certificate chain
+
+    - `privkey.pem` — private key
+
+Create the directory to put the certificates in (inside the mailserver directory):
+```bash
+mkdir config
+mkdir config/ssl
+```
+Now You can copy the certificates into the directory:
+```bash
+sudo cp /etc/letsencrypt/live/mail.example.com/fullchain.pem config/ssl/
+sudo cp /etc/letsencrypt/live/mail.example.com/privkey.pem config/ssl/
+
+## Step 3: Create docker-compose.yml
+```yaml
+version: '3.8'
+
+services:
+  mailserver:
+    image: mailserver/docker-mailserver:latest
+    hostname: mail
+    domainname: example.com
+    container_name: mailserver
+    ports:
+      - "25:25"      # SMTP
+      - "143:143"    # IMAP
+      - "587:587"    # Submission (SMTP with STARTTLS)
+      - "993:993"    # IMAPS (IMAP over SSL)
+    volumes:
+      - maildata:/var/mail
+      - mailstate:/var/mail-state
+      - ./config/:/tmp/docker-mailserver/
+      - ./config/ssl/:/etc/letsencrypt/live/mail.example.com/:ro
+    environment:
+      - ENABLE_SPAMASSASSIN=1
+      - ENABLE_CLAMAV=1
+      - ENABLE_FAIL2BAN=1
+      - ENABLE_POSTGREY=1
+      - ONE_DIR=1
+      - DMS_DEBUG=0
+      - SSL_TYPE=manual
+      - SSL_CERT_PATH=/etc/letsencrypt/live/mail.example.com/mail.example.com.crt
+      - SSL_KEY_PATH=/etc/letsencrypt/live/mail.example.com/mail.example.com.key
+      - SSL_DHPARAM_PATH=/etc/letsencrypt/live/mail.example.com/dhparam.pem  # Optional
+    restart: always
+
+volumes:
+  maildata:
+  mailstate:
+```
+
+## Step 4: Add DH-Parmeters (recommended)
+```bash
+openssl dhparam -out ./config/ssl/dhparam.pem 2048
+```
+DH parameters strengthen SSL security by enabling perfect forward secrecy during key exchange. Generating your own DH parameters helps prevent some cryptographic attacks.
+
+## Step 5: Start Container
+```bash
+docker-compose up -d
+```
+The logs will show errors about there having to be at least one mail account, this one will be created in the next step
+
+## Step 6: Create Mail Account
+```bash
+docker exec -it mailserver setup email add user@example.com password
+```
+OR
+```bash
+docker exec -it mailserver setup email add user@example.com
+```
+If You don't want the password to be saved in your command history. You will be prompted for a password right after hitting enter
+
+## Step 7: Verify SSL/TLS
+```
+openssl s_client -connect mail.example.com:993
+openssl s_client -starttls smtp -connect mail.example.com:587
+```
+
+## Step 8: Add Email Aliases
+First, create the alias file:
+```bash
+nano config/postfix-virtual.cf
+```
+Now You have multiple options:
+- Single Email alias:
+    ```text
+    admin@example.com      me@example.com
+    ```
+- Catch-All alias
+    ```text
+    @example.com           me@example.com
+    ```
+The file can contain multiple aliases, one per line
+
+Now add the following Env variable to the docker-compose file if not already set:
+```yaml
+environment:
+  - ENABLE_POSTFIX_VIRTUAL_TRANSPORT=1
+```
+
+Finally, restart the docker container:
+```
+docker-compose up -d
+```