Mailcow

Mailcow is a popular open source mail server suite that bundles Postfix, Dovecot, Rspamd, ClamAV, and SOGo into a single Docker stack with a clean, modern web admin UI. It is a strong self-hostable alternative to Gmail, Microsoft 365, and Google Workspace for organisations that want full control of their email.

Mailcow supports unlimited mailboxes, domains, and aliases, with quarantine, sieve filters, ActiveSync (via SOGo), full-text search, and standard email protocols (SMTP, IMAP, POP3). Out-of-the-box it ships with DKIM, SPF, DMARC, and TLS enforcement, plus a built-in fail2ban-style ratelimiter for abuse protection.

Released under GPL-3.0, Mailcow is widely used by SMBs, schools, and privacy-focused organisations that want a production-ready mail server they can deploy in under an hour, on a single VM or bare-metal host.