18 self-hosted Rackspace Email alternatives

Production-ready mail server stack in a Docker container with SMTP, IMAP/POP3, LDAP auth, anti-spam/AV, DKIM/DMARC, and optional OAuth2 support.

18.8k stars2k forksMITlast commit 24 Aug 2026Actively maintained

Mail-in-a-Box is a one-click mail server appliance for Ubuntu, bundling SMTP/IMAP, webmail, DNS, TLS automation, backups, and an admin control panel.

15.4k stars1.5k forksCC0-1.0last commit 21 Aug 2026Actively maintained

All-in-one open-source mail and collaboration server with SMTP, IMAP, JMAP, CalDAV, CardDAV, and WebDAV, plus integrated anti-spam and phishing protection.

14.4k stars909 forkslast commit 25 Aug 2026Actively maintained

Mailcow is a dockerized mail server suite providing SMTP/IMAP, webmail, anti-spam/anti-virus, and domain/mailbox administration via a unified web UI.

13.3k stars1.8k forksGPL-3.0last commit 18 Aug 2026Actively maintained

Mailu is a full-featured mail server distributed as Docker images, providing SMTP/IMAP/POP3, webmail, administration UI, and built-in security and anti-spam features.

7.5k stars997 forkslast commit 17 Aug 2026Actively maintained

Go-based, modular mail server implementing SMTP/LMTP/IMAP with built-in DKIM/SPF/DMARC, storage backends (SQLite/Postgres/S3), Prometheus metrics and Docker support.

6.1k stars326 forksGPL-3.0last commit 13 Jul 2026Actively maintained

All-in-one secure mail server with SMTP, IMAP, webmail, automatic TLS (ACME), and built-in SPF/DKIM/DMARC plus junk filtering for low-maintenance domains.

5.8k stars218 forksMITlast commit 23 Aug 2026Actively maintained

Modoboa is an open source mail server management platform with a modern web UI, integrating Postfix and Dovecot with admin tools, webmail, calendar, and address book.

3.5k stars481 forksISClast commit 26 Aug 2026Actively maintained

A Bash script that auto-implements a full mail server (Postfix, Dovecot, DKIM, SpamAssassin) with TLS and PAM-based logins on Debian/Ubuntu.

2.2k stars341 forksGPL-3.0last commit 4 May 2025Slowing down

WildDuck is a horizontally scalable IMAP/POP3 mail server that stores all mail in MongoDB, runs stateless Node.js workers, and provides a REST API for full server control.

2.1k stars278 forksEUPL-1.2last commit 26 Aug 2026Actively maintained

Automated open-source mail server installer bundling Postfix, Dovecot, webmail, anti-spam/antivirus and LDAP/SQL backends for mainstream Linux/BSD.

1.8k stars260 forksGPL-3.0last commit 27 Aug 2026Actively maintained

High-performance, standards-compliant IMAP/POP3/LMTP server with flexible authentication, extensible plugin system (Lua, Sieve) and OpenSSL TLS support.

1.2k stars347 forkslast commit 24 Aug 2026Actively maintained

Cyrus IMAP is a secure, scalable mail server providing IMAP/JMAP email plus CalDAV/CardDAV contacts and calendars, with ACLs, quotas, search, and replication.

643 stars175 forkslast commit 26 Aug 2026Actively maintained

Citadel is an open source groupware and messaging server providing email, calendars, contacts, and a web interface with room-based collaboration.

Activity unknown

Courier is an integrated mail server suite providing ESMTP (MTA), IMAP, POP3, webmail, and mailing lists with optional LDAP/MySQL/PostgreSQL-backed virtual accounts.

Activity unknown

Open-source webmail and groupware offering email, contacts, calendar, cloud drive, tasks, notes and an admin control panel for multi-tenant email services.

Activity unknown

Simple NixOS Mailserver provides NixOS modules to deploy a full email server with SMTP/IMAP, spam filtering, DKIM/DMARC/SPF, and TLS automation.

Activity unknown

Self-hosted enterprise collaboration suite providing email, webmail, calendaring, contacts, and administration for organizations.

Activity unknown