Postaci (Turkish for Postman) is multiplatform Webmail software which is database independent, multilanguage, POP3/IMAP, and fully MIME-compatible. While using POP3 mode to fetch messages it uses database fields to simulate IMAP folders, on which you can save, move, delete, and read e-mail. It also contains an adressbook, a notebook, and a bookmark manager application.
Quotient is multi-protocol (SMTP, POP, IMAP, SIP, HTTP, Q2Q) server that helps with all your online conversations, be they over email, IRC, IM, mailing lists, or voice over IP. It is written in Python on the Twisted framework, and uses Xapian for search and SpamBayes for spam classification.
The Gordano Messaging Suite (GMS) is a highly flexible and reliable suite of messaging products. Customers can choose which components meet their needs from email, Webmail, collaboration, instant messaging, calendaring, SMS, and list server software all of which can be complimented by high level anti-spam, anti-virus, and archiving options.
Webtop is a Web-based POP3 email client that includes SSL encryption, Mozilla support, many email filter options, spam fighting features, custom folders, email import/export, fast searching, undeliverable email bounce, intelligent read receipts, and email-to-PDF generation. The Webtop also includes a calendar, notepad, online file storage, automated email reminders, contacts, mailing lists, and Web-based administration. One installation can support multiple users and each user can set up as many POP3 accounts as they need.
XFMail is an X11 application for receiving electronic mail. It implements most of its email functionality internally so that it does not depend on a lot of extra packages. It supports POP3, MBOX, IMAP4, sendmail, and SMTP. It has built-in support for interfacing with PGP, GPG, ispell/aspell, faces, LDAP, and esound. It runs on most Unix variants.
Althea is an IMAP email client for X that uses the GTK widget set. It was built with the IMAP protocol in mind in order to avoid many of the pitfalls experienced by POP clients that added IMAP support. Althea allows easy access to a nearly unlimited number of servers, and has a very small memory footprint. As of version 0.5.0 Althea also supports IMAP over SSL.
oMail-webmail is a Webmail solution for mail servers based on qmail and optionally vmailmgr or vpopmail. The mail is read directly from maildirs on the hard disk, which is much quicker than using protocols like POP3 or IMAP. Other features includes multiple language support (English, French, German, Japanese, Chinese, and many more), HTML and pictures inline display, folders, and address book support.
Inverse SOGo Connector for Thunderbird is an extension which transforms Thunderbird into a full DAV client for groupware servers such as SOGo, OpenGroupware.org, and Citadel. It does this by adding support for remote DAV address books and by adding features to be used along with the Lightning calendar extension. It is a merge of the Lightning Enhancer and the GroupDAV Addressbook Connector.
isync is a commandline application which synchronizes a local maildir-style mailbox with a remote IMAP4 mailbox, suitable for use in IMAP-disconnected mode. Multiple copies of the remote IMAP4 mailbox can be maintained, and all flags are synchronized. TLS/SSL is supported via imaps: or STARTTLS.