iRedMail

A fully fledged, free email server solution, an open source project (GPL v2). Use official binary packages from Linux/BSD distributions, with both i386 and x86_64 support. Easy, fast deployment in LESS THAN 1 MINUTE.

Free Open Source Linux BSD Self-Hosted

Dovecot

Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like systems, written with security primarily in mind. Dovecot is an excellent choice for both small and large installations.

Free Open Source Mac OS X Linux

Cyrus IMAP

The Cyrus IMAP server differs from other IMAP server implementations in that it is generally intended to be run on sealed servers, where normal users cannot log in.

Free Open Source Mac OS X Linux

Courier IMAP

The Courier IMAP server is a fast, scalable, enterprise IMAP server that uses Maildirs. Many E-mail service providers use the Courier IMAP server to easy handle hundreds...

Free Open Source Mac OS X Linux BSD Self-Hosted

Archiveopteryx

Archiveopteryx stores email in a database and provides access to it through IMAP and more.

Free Open Source Mac OS X Linux BSD