ADJE WebMail is a set of Perl CGI scripts which provide a Web interface to existing email accounts on any POP3-compliant email server. The software provides a complete interface, including encoding/decoding attachments, email and URL markup in received emails, and an address book for each user.
AfterLogic WebMail Lite PHP is a Webmail script with a modern AJAX interface. It supports IMAP accounts, SMTP, and SSL (including Gmail). Users can check and send mail and use an address book. It provides a slick skin, a three-pane view, non-English language support, UTF-8 support, IMAP folders, and viewing and composing HTML mail. A MySQL backend is supported, with Web-based administration and installation and cPanel/Plesk/DirectAdmin integration.
AfterLogic XMail Server is an email server. It supports ESMTP, TLS/SSL secure connections, SMTP authentication, account and domain aliasing, anti-spam features (IP-based and email address based), mailing lists, logging, remote administration, the Finger protocol, filters, and custom mail processing. AfterLogic XMail Server is based on the XMail server, but features simultaneous multi-user access to a POP3 mailbox, the ability to configure port numbers via a configuration file, a Windows installer, and a Web administration tool with an AJAX interface.
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.
The AmavisNewSQL SquirrelMail plugin gives you per-user control of a subset of SpamAssassin settings which are stored in a database. It also allows you to use a quarantine database for questionable mail. This plugin was designed with enterprise use in mind, and differs from other plugins in that it works with amavis-new rather than SpamAssassin directly. Most of the code lives in an external class that you can reuse in your own admin tools. It even has support for SOAP calls to perform common tasks.
Arrow is an elegant, powerful, graphical interface to electronic mail. This is not just another single window mail reader. Instead, it displays each mailbox and message in a separate window, thereby allowing one to simultaneously open as many mailboxes and view and compose as many messages as one wishes. This paradigm also allows one to drag-and-drop text between messages and organize ones mail by dragging messages between mailboxes.