DockMail

DockMail is a lightweight, Docker-based email server solution using OpenSMTPD for SMTP and Dovecot for IMAP. It supports DKIM for email security and includes Roundcube as a web-based client.

Features

• Lightweight: Optimized for performance with minimal components.
• Secure: Built-in DKIM support for email integrity.
• User-Friendly: Webmail access via Roundcube for a modern interface.

Installation Guide

Prerequisites

• Ensure that Docker, Docker Compose 2.x.x, and Nginx are installed and properly configured to avoid compatibility issues.

Step 1: Configure DNS Records

1.1 A Records for Mail Services

Ensure that the following A records are configured in your DNS:

Subdomain	Type	Value
mail.example.com	A	<server IP>
smtp.example.com	A	<server IP>
imap.example.com	A	<server IP>

• Replace <server IP> with the IP address of your server where DockMail is deployed.
• If you are using Cloudflare DNS, the mail subdomain can be proxied, but smtp and imap subdomains must not be proxied.
• The mail subdomain can be different from the smtp and imap subdomains; they do not have to share the same domain name.

1.2 MX Record

Add the following MX record to ensure that emails sent to your domain are correctly routed to the SMTP server:

Name	Type	Priority	Value
example.com	MX	10	smtp.example.com

1.3 SPF Record

Add an SPF record to specify which mail servers are allowed to send emails on behalf of your domain:

Name	Type	Value
example.com	TXT	v=spf1 a mx ip4:<server IP> -all

Step 2: Configure Nginx for Webmail and Certbot

Below are two separate Nginx configurations: one for handling Webmail traffic and another for Certbot's SSL validation.

2.1 Nginx Configuration for Webmail

server {
    listen 80;
    server_name mail.example.com;

    root /path/to/webmail/webroot;
    index index.php index.html;

    location / {
        try_files $uri $uri/ /index.php?$args;
    }
    location ~ \.php$ {
        include fastcgi_params;
        fastcgi_pass 127.0.0.1:8999;
        fastcgi_param SCRIPT_FILENAME /var/www/html$fastcgi_script_name;
        fastcgi_param DOCUMENT_ROOT /var/www/html;
    }
    location ~ /\.ht {
        deny all;
    }
}

2.2 Nginx Configuration for Certbot HTTP-01 Validation (SMTP and IMAP)

server {
    listen 80;
    server_name smtp.example.com imap.example.com;

    location /.well-known/acme-challenge/ {
        alias /path/to/certbot/webroot/.well-known/acme-challenge/;
    }
    location / {
        deny all;
    }
}

• Explanation: This configuration allows Certbot to perform HTTP-01 validation for SSL certificates by redirecting .well-known/acme-challenge/ requests to Certbot’s service.

Step 3: Execute the initialize.sh Script

The initialize.sh script sets up SSL certificates for the IMAP and SMTP subdomains and modifies the OpenSMTPD configuration to use the provided domain.

3.1 Run the Script

1. Make the script executable:

   chmod +x initialize.sh

2. Run the script:

   ./initialize.sh

3. After successful execution:

   • SSL certificates will be generated for imap.example.com and smtp.example.com.
   • OpenSMTPD configuration will be updated with your specified domain.

3.2 Script Functions

• Generate SSL certificates for imap.example.com and smtp.example.com using Certbot.
• Update OpenSMTPD configuration with the specified domain.

3.3: Open Firewall Ports

To ensure that your mail services are accessible, make sure to open the following ports in your server's firewall:

• Port 25: For SMTP communication.
• Port 587: For SMTP with STARTTLS.
• Port 143: For IMAP.
• Port 993: For IMAPS.

You can use the following commands to open these ports (assuming ufw as the firewall tool):

sudo ufw allow 25
sudo ufw allow 587
sudo ufw allow 143
sudo ufw allow 993
sudo ufw reload

Step 4: Start and Verify Docker Services

Start the email server:

docker compose up -d

• Verify that all services are running:

docker compose ps

Ensure that OpenSMTPD, Dovecot, and Webmail containers are running without errors.

4.1 Troubleshooting

If any service is not running or encounters an error, use the following command to check detailed logs:

docker compose logs -f [service_name]

For example:

docker compose logs -f opensmtpd

Step 5: Configure DKIM Public Key in DNS

The public DKIM key is generated during the setup process and can be found in the following file:

sudo cat opensmtpd/rspamd/keys/mail._domainkey.example.com.txt

Copy the content of this file and add it as a TXT record in your DNS settings:

Name	Type	Value
mail._domainkey	TXT	"v=DKIM1; k=rsa; p=<public_key>"

Make sure to replace <public_key> with the Base64-encoded public key found in the file.

Step 6: Add Users

The dockmail.sh script provides a convenient way to manage users (add, delete, modify, list) in the DockMail system.

6.1 Make the script executable

First, make the script executable:

chmod +x dockmail.sh

6.2 Run the script to add a new user

To add a new email user, execute:

./dockmail.sh

• Follow the prompts to enter the username, password, and optional nickname.

6.3 Script Functions

• Add User: Create a new user with specified username and password.
• Delete User: Remove an existing user from the database.
• Change Password: Update the password for an existing user.
• Modify Nickname: Update the user's nickname.
• List Users: Display a list of existing users.

Additional Information

• To verify the DKIM setup, you can use DKIM Validator or similar tools.
• For troubleshooting, check the logs of individual services using:

docker compose logs -f opensmtpd
docker compose logs -f dovecot
docker compose logs -f webmail

Advanced Configuration

Add an Alias

To add an email alias, for example enabling both main@example.com and alias@example.com to receive mail in the same inbox:

1. Update Database: Add "alias@example.com" to the aliases JSONB field for main@example.com user.
2. Create Mail Link: Set up the mail directory link in Dovecot:

docker exec dovecot ln -s /var/mail/main@example.com /var/mail/alias@example.com

Set Webmail Theme

To customize the webmail interface theme:

1. Add Theme: Place the theme folder in webmail/webroot/skins/ directory.
2. Configure Theme: Set ROUNDCUBEMAIL_SKIN in webmail/.env to your theme name.