Mailcow on the Server

Mailcow (mailcow: dockerized) is a ready-to-use open-source stack for deploying your own corporate or private mail server. Unlike manually configuring Postfix + Dovecot + SpamAssassin, Mailcow bundles all components into Docker containers and provides a convenient web interface for administration.

Mailcow Components

• Postfix — Mail Transfer Agent (MTA)
• Dovecot — IMAP/POP3 server and Sieve filters
• SOGo — Webmail (email, calendar, contacts)
• Rspamd — Spam protection
• ClamAV — Antivirus scanning for attachments
• ACME / Let's Encrypt — Automatic SSL certificates
• Unbound — Local recursive DNS server
• Web Admin UI — Management panel

Requirements

• Clean Linux OS (Ubuntu 22.04 / 24.04 recommended)
• Minimum 4 GB RAM (6 GB+ recommended for stable operation)
• Root access
• Open ports: 25, 80, 110, 143, 443, 465, 587, 993, 995, 4190
• Configured DNS records: A, MX, SPF (TXT), DKIM (TXT), and reverse PTR (rDNS)

Installation — Command Breakdown

Step 1: Update the System

apt update && apt upgrade

• apt update — refreshes the local package index from connected repositories
• && — runs the next command only if the first succeeds
• apt upgrade — upgrades installed packages to the latest versions

Step 2: Install System Utilities

apt install ca-certificates curl gnupg -y

• ca-certificates — root certificates for SSL/TLS connections
• curl — file downloads and HTTP requests from the terminal
• gnupg — GPG/PGP key management
• -y — auto-confirm installation prompts

Step 3: Create Keyrings Directory

install -m 0755 -d /etc/apt/keyrings

Creates the directory for external repository GPG keys with rwxr-xr-x permissions.

Step 4: Import Docker GPG Key

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /etc/apt/keyrings/docker.gpg

Downloads the Docker signing key and saves it in binary format.

Step 5: Add Official Docker Repository

echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu $(. /etc/os-release && echo $VERSION_CODENAME) stable" | tee /etc/apt/sources.list.d/docker.list >/dev/null

Automatically detects CPU architecture and OS codename, binds the signing key for package verification.

Step 6: Install Docker

apt update && apt install docker-ce docker-ce-cli containerd.io -y

Step 7: Manage Docker Service

systemctl start docker
systemctl enable docker

• systemctl start docker — starts the Docker daemon
• systemctl enable docker — enables autostart on reboot

Step 8: Install Docker Compose (Standalone)

sudo curl -L "https://github.com/docker/compose/releases/download/v2.20.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose

Downloads Docker Compose v2.20.2 binary for the current architecture and makes it executable.

Step 9: Fix Key Permissions

chmod a+r /etc/apt/keyrings/docker.gpg

Grants read access to the Docker key for all users — required for APT.

Step 10: Install jq

apt install jq -y

jq is a JSON parser used by Mailcow scripts for configuration handling.

Step 11: Clone Mailcow Repository

git clone https://github.com/mailcow/mailcow-dockerized
cd mailcow-dockerized

Clones the official repository into the mailcow-dockerized directory.

Step 12: Generate Configuration

./generate_config.sh

Interactive script prompts for mail server FQDN (e.g. mail.yourdomain.com), timezone, and update branch. Creates mailcow.conf with random database passwords and keys.

Step 13: Start Mailcow

docker compose up -d

• docker compose up — pulls images and starts all containers from docker-compose.yml
• -d — detached (background) mode

After Launch

1. Open your mail domain in a browser: https://mail.yourdomain.com
2. Default admin credentials: admin / moohoo
3. Change the default admin password immediately!

DNS and Ports

Ensure these ports are open: 25, 80, 110, 143, 443, 465, 587, 993, 995, 4190.

Configure DNS records:

FAQ

How much RAM does Mailcow need?

Minimum 4 GB; 6 GB or more is recommended for stable operation of all containers.

Can I install it on Windows?

No. Mailcow runs only on Linux with Docker.

Which OS is supported?

Ubuntu, Debian, and other Docker-compatible Linux distributions. This guide uses Ubuntu.

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