fdm (fetch and deliver mail) is a simple, lightweight replacement for mail fetching, filtering, and delivery programs such as fetchmail and procmail. It can fetch using POP3, POP3S, IMAP, IMAPS, or stdin, and deliver to a pipe, file, maildir, mbox, or SMTP server, based on a set of regexps. It can be used for both single user and multiuser setups, and is designed with privilege separation when running as root.
ZMailer is an internet message transfer agent. It is intended for gateways or mail servers or other large site environments that have extreme demands on the abilities of the mailer. It was motivated by the problems of the Sendmail design in such situations. It is intended and designed as a multi-protocol mailer. The only protocol supported in this distribution is RFC822 (and variations).
aptg(2) (a place to go) is a Web-based email client written in PHP, using localhost connections to a running IMAP4 server. It is designed to work with Postfix. Authentication is against a MySQL database as used by pam_mysql (username + password) or by using one of the virtual email addresses (also stored in the MySQL database) and that password. A powerful addressbook is also included. It uses its own session handling system with one-time session ids. The development version has experimental GnuPG support.
kmMail is a PHP-based mail program, based on the mail functionality of Keftamail and is being developed by current Kefta employees. It is meant to be a framework for putting a web-based mail program on your site, but is still robust enough to drop into your current site with little to no modification. The goals of kmMail are MIME compliance, speed, low overhead, and an enjoyable user interface.
Virtual Exim is a PHP-enabled Web interface for managing multiple virtual mail domains with Exim and MySQL/PostgreSQL. POP/IMAP accounts, aliases, forwards, and permanent fail accounts can all be created and managed easily without the need for corresponding shell accounts. Virtual Exim also allows the server administrator to designate a SiteAdmin who can create and delete domains on the fly through the interface, so no editing of the Exim configuration file is required. Individual users can also log in to change their "Real Name", passwords, and mail filtering options with ease.