Pronto! is a full-featured mail client written in Perl/GTK+, and a continuation of the development of CSCMail project in Perl. It supports multiple POP3/maildir and mbox accounts, imports/exports MBOX, and has full search features and VFolders, sortable filters, threaded message list, a nested folder list, drag and drop, and inbound and outbound attachments.
Claros inTouch is an AJAX Web mail, instant messenger, address book, and note taker application. The main features are drag and drop support, background attachment uploading, built-in Bayesian spam protection that can identify junk mail on the fly, folder support for the POP3 protocol, compatibility with any POP3/IMAP and SMTP server, operating system independence, support for sending HTML email, and full MIME compatibility. It also features a unique AJAX instant messenger that is capable of talking with a Jabber server.
VAMP (Very Attractive Mail Program) is an extremely easy-to-configure, usable, Web-based email client written in PHP3 (and compatible with PHP4). It is for use with POP3 servers, and it also supports "Virtual Domains", encryption (under Linux/PHP3), attachments, contact list, a signature database, an easy-to-use setup tool, and more.
sYnergy is a Web-based groupware and communication solution for use with an intranet. It includes email mailboxes, a fax viewer and sending function, contact lists, an appointment and task management function, a picture database, and a function for listening to voice messages. The extensive user management enables administrators to assign various permissions to each user and to exchange data e.g. contacts, appointments, or tasks. It also offers a function to import existing data.