This is the University of Washington's IMAP source distribution, which includes the IMAP4rev1 server, as well as a POP server that, in addition to offering the normal POP service, can relay commands to an IMAP server, thus permitting existing POP clients to access an IMAP server.
NullLogic Groupware is a modular Web-based groupware and email system designed for contact management and event scheduling. Additional features include private messaging, public discussion forums, webmail, shared bookmarks, file sharing, call tracking, order processing, an XML-RPC API, and integrated POP3 and SMTP servers.
Scalix Community Edition Raw (CE Raw) is functionally equivalent to Scalix's Community Edition software except that its components are individually available, making it easy to customize. It includes manual installation instructions via a community Wiki, with links to required third-party components. It is available for the Debian Linux distribution as well as Red Hat and SUSE Linux. The intent is to make it easy for Linux system admins, developers, and enthusiasts to to adapt an email and calendaring system for their needs and the needs of the community.
TigerCube is an operating system that offers an all-in-one communications platform (including an advanced phone system and email), network security (with a firewall, content filtering, and virtual private networking), file sharing, and a fully integrated backup solution under a single, unified environment. TigerCube is free to use for up to 5 users.