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mailcow

LicenseFOSS problemsMaintenanceSSOUsersTested
GPLv3—Active✅Unlimited❌

Description​

mailcow (mailcow: dockerized) is a full self-hosted mail server stack, not a single application — Postfix for SMTP, Dovecot for IMAP/POP3, SOGo for webmail and groupware (calendar, contacts), Rspamd for spam filtering, and ClamAV for antivirus, run as a set of Docker containers behind one admin UI.

Features​

  • One admin UI over many services — mailbox/domain management, DKIM, quarantine, and Rspamd's spam scoring all surface through mailcow's own web UI instead of each component's native tooling.
  • SOGo webmail and groupware — calendar (CalDAV) and contacts (CardDAV) alongside IMAP webmail, not just an inbox.
  • External identity provider login — an OIDC integration lets an existing IdP authenticate mailbox users alongside mailcow's own SQL-backed accounts, one provider at a time.

Usage patterns​

  • Full mail stack for a domain that wants to own its own inbox — receiving, sending, spam filtering, and webmail under one deployment, not just outbound transactional email.
  • Genuinely multi-container — Postfix, Dovecot, SOGo, Rspamd, ClamAV, Solr (search), Redis, and MySQL/MariaDB each run as their own container; mailcow's compose file and admin UI are what make operating that stack as one product tractable.

License and governance​

GPLv3 — free and open source, no enterprise-tier feature gate. Maintained by The Infrastructure Company GmbH, which also holds the mailcow trademark — single-vendor governed, not foundation-backed, the same shape flagged elsewhere in this catalog, though the license itself carries no relicensing risk to what's already released.

Conclusion​

Why you would — a real inbox under your own domain, not just outbound email, with spam filtering, antivirus, webmail, and calendar/contacts bundled in, fully GPL with nothing held back behind a paid tier.

Why you wouldn't — mail is one of the least forgiving self-hosted services to run wrong: deliverability depends on DNS (SPF/DKIM/DMARC, PTR records) and IP reputation as much as the software, and this is a genuinely multi-container stack to keep patched and monitored, not a single service.