Knowledge Base

Mailcow is a modern, open source, and Docker-based email server solution. It combines components such as Postfix, Dovecot, SoGo, and Rspamd into a single Docker structure, offering a powerful and fully-featured mail platform. It can operate independently of hosting control panels like Plesk. In this article, we will explain in detail how to configure Mailcow from scratch, along with the Docker infrastructure, and performance & security optimizations.

1. Requirements

• Ubuntu 20.04/22.04 or Debian 11+ is recommended.

• At least 2 vCPU, 4 GB RAM, 40+ GB disk space

• root SSH access

• Domain name (e.g., mail.yourdomain.com) and DNS control

• Docker and Docker Compose must be installed

2. Installing Docker and Docker Compose on the Server

apt update && apt upgrade -y
apt install curl git docker.io docker-compose -y
systemctl enable docker --now

3. Downloading and Starting Mailcow

cd /opt
git clone https://github.com/mailcow/mailcow-dockerized
cd mailcow-dockerized
cp mailcow.conf.example mailcow.conf

mailcow.conf Settings:

• MAILCOW_HOSTNAME=mail.yourdomain.com

• TZ=Europe/Istanbul

• SKIP_LETS_ENCRYPT=n

• ADDITIONAL_SAN=webmail.yourdomain.com

4. DNS Settings

Create the following records from your DNS management panel:

5. Starting the Docker Service

./generate_config.sh
sudo docker compose pull
sudo docker compose up -d

You can access the Mailcow interface at:

https://mail.yourdomain.com

Default user:

admin / moohoo

6. Firewall and Ports

The following ports must be opened:

• 25 (SMTP)

• 587 (Submission)

• 993 (IMAP SSL)

• 465 (SMTPS)

• 80, 443 (Webmail, Let’s Encrypt)

ufw allow 25,465,587,993,80,443/tcp

7. Optimization and Security Settings

A) Create Swap Space (for RAM insufficiency)

fallocate -l 2G /swapfile
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
echo '/swapfile none swap sw 0 0' >> /etc/fstab

B) Fail2ban + Rspamd Brute Force Blocking

Mailcow Rspamd integrates anti-spam, greylisting, rate limit, and brute force protections. Installing Fail2Ban is recommended:

apt install fail2ban -y

C) Daily Automatic Update (Optional)

0 4 * * * cd /opt/mailcow-dockerized && ./update.sh --force-pull && docker compose up -d

D) Docker Resource Usage Limiting (In Docker compose.yml):

    mem_limit: 512m
    cpus: 0.5

8. Usage on External Servers Without Plesk

Mailcow operates independently without the need for panels like Plesk or cPanel. If you wish, you can provide only email service under mail.yourdomain.com and host your website on a different server.

If you are using Plesk:

• Websites run on the Plesk server, and Mailcow runs on a separate VPS/dedicated server.

• DNS records should be directed to the Mailcow IP (MX, A, SPF, DKIM).

9. Backup Recommendation

docker exec -it mysql-mailcow mysqldump -u root -p mailcow > mailcow-backup.sql
tar czf /root/mailcow-full-backup.tar.gz /opt/mailcow-dockerized

Mailcow, with its Docker-based structure, provides a flexible, modern, and secure mail server. It is ideal for users who want full control without the need for Plesk or similar panels. It can be easily used in both small-scale and corporate systems. You can create a powerful email infrastructure with correct configuration and DNS integration.