WebCit is a Web-based, AJAX-enabled frontend to the Citadel groupware/collaboration system. It is an attractive Web middleware layer that allows user-friendly access. By combining WebCit and Citadel, you can have a versatile online environment with many users concurrently accessing the same system using the user interface of their choice (text, Web, or downloaded client software).
Mahogany is a GUI email client for the X11/Unix, Windows, and Mac platforms. It supports a wide range of Internet protocols (IMAP4, POP3, ESMTP, NNTP) and encrypted communications using SSL, includes full MIME support, and aims to be fully standard-compliant. It allows the use of unlimited number of servers, supports filters and identities, and offers optional HTML viewing and much more.
MailMan is one of the most stable, mature, and robust Web-based email systems available. The overall goal of the system is to provide the simplest possible way to add a Web-based email system to any Web site, so ease of installation and maintenance was the first goal in MailMan's design. It has no dependencies and no known incompatibilities with any Web server or mail server. It supports sending and receiving attachments, a single-frame or multi-frame interface, HTML-formatted messages, user options, address books, mail folders, and more.
GNU Mailutils is a rich and powerful protocol-independent mail framework. It contains a series of useful mail libraries, clients, and servers. These are the primary mail utilities for the GNU system. The central library is capable of handling electronic mail in various mailbox formats and protocols, both local and remote. Specifically, this project contains a POP3 server, an IMAP4 server, and a Sieve mail filter. It also provides a POSIX "mailx" client and a collection of other handy tools.