Mailcow — Dockerized Email Server with Web Administration

Introduction

Mailcow is an open-source mail server suite that packages all the components needed to run a production email service into Docker containers. It provides a polished web UI for managing domains, mailboxes, aliases, DKIM signing, spam filtering, and antivirus scanning without manual configuration of each underlying service.

What Mailcow Does

• Deploys a complete SMTP/IMAP/POP3 mail server stack via a single docker-compose file
• Provides a responsive web administration panel for domain, mailbox, and alias management
• Includes SOGo for webmail, calendar, contacts, and ActiveSync device support
• Integrates Rspamd for spam filtering and ClamAV for antivirus scanning out of the box
• Handles DKIM, SPF, DMARC, and TLS certificate management automatically with ACME support

Architecture Overview

Mailcow orchestrates over a dozen Docker containers: Postfix handles SMTP relay and delivery, Dovecot provides IMAP and POP3 access, SOGo serves as the groupware frontend, Rspamd classifies spam, ClamAV scans attachments, and Nginx terminates TLS. A central MySQL database stores configuration, while Redis handles caching and rate limiting. The mailcow UI communicates with each service through APIs and configuration templating.

Self-Hosting & Configuration

• Requires a Linux host with Docker and Docker Compose, a public IP, and valid DNS records (MX, SPF, DKIM, DMARC)
• Run generate_config.sh to set hostname, timezone, and initial admin credentials
• Access the admin UI at https://mail.yourdomain.tld after startup to add domains and mailboxes
• Configure backup schedules and retention via the built-in backup script or external snapshot tools
• Update by running ./update.sh which pulls new images and applies migrations automatically

Key Features

• All-in-one deployment: SMTP, IMAP, webmail, groupware, antivirus, and spam filtering in one stack
• Modern admin UI with per-domain and per-mailbox quotas, rate limiting, and logging
• SOGo groupware with full ActiveSync support for mobile device synchronization
• Built-in quarantine management for reviewing and releasing spam-flagged messages
• ACME integration for automatic Let's Encrypt TLS certificate provisioning and renewal

Comparison with Similar Tools

• Mail-in-a-Box — installs directly on the host OS; Mailcow uses Docker for easier isolation and updates
• Mailu — similar Docker approach but lighter; Mailcow includes richer groupware via SOGo and a more feature-complete admin UI
• iRedMail — script-based installer for bare metal; Mailcow's containerized design simplifies backup and migration
• Docker Mailserver — minimalist container setup; Mailcow provides a web UI and integrated groupware out of the box
• Stalwart — modern Rust-based server; Mailcow offers a more mature ecosystem with proven groupware integration

FAQ

Q: What DNS records do I need before installing? A: At minimum, an A record for your mail hostname, an MX record pointing to it, and SPF/DKIM/DMARC TXT records. Mailcow's documentation provides exact record templates.

Q: Can Mailcow handle multiple domains? A: Yes. You can add unlimited domains through the admin UI, each with independent mailboxes, aliases, and DKIM keys.

Q: How do I back up my mail data? A: Mailcow includes a backup script that snapshots the database, mail storage, and encryption keys. Schedule it via cron for automated backups.

Q: Does it support two-factor authentication? A: Yes. The admin panel and SOGo webmail both support TOTP-based two-factor authentication.

Sources

• https://github.com/mailcow/mailcow-dockerized
• https://docs.mailcow.email/