postfix_memcached is a patch to Postfix (2.1 and 2.2) to allow it to use memcache as a map source. The memcache map type can be used to reduce the load on another map type, e.g. pgsql. By placing the memcache map before the pgsql map, a key not found in the memcache will fall through to the database. You'll need to figure out a way to reverse populate the cache from the database yourself. This map type can be seen as an alternative to the proxymap(8) service.
Jsmtpd is a small and modular SMTP server daemon. It is heavily based on plugins, and currently supports spam detection (Spamassassin, Jasen, RBL servers, and BlackList), anti-virus (Clam Antivirus), Recipient rewriting, and many other filters. Filtering is done with a customisable tree of filters. Almost all functionality is implemented as plugins, making it easy to fit your needs.
AXIGEN is a fast, reliable and secure mail server with an open architecture. It is designed for easy management and allows full control of the email traffic from a central Web/CLI admin module. AXIGEN provides ESMTP, IMAP, and POP3 services and has been tested with standard mail clients. A special Webmail module enables email access and delivery from Web browsers. During the evaluation period, users are provided with full technical support.
Kolab is a groupware system that provides a comprehensive and flexible solution for workgroups. Email, contacts, and group calendars can be managed via the Web, Windows/Outlook, and Linux/KDE. It supports offline synchronization and full seamless support of mixed client environments because the Kolab-XML storage format is fully open and avoids MAPI/TNEF.
sendmail X is a modularized message transfer system consisting of five (or more) persistent processes, four of which are multi-threaded. A central queue manager controls SMTP servers and SMTP clients to receive and send email messages, an address resolver provides lookups in various maps (including DNS) for mail routing, and a main control program starts the others processes and watches over their execution. The queue manager organizes the flow of messages through the system and provides measures to avoid overloading the local or remote systems by implementing a central control instance. sendmail X is simple to configure using a syntax that is easy to understand and use. It is intended to be used as a secure and efficient mail gateway. It does not provide any mail content modification capabilities such as address masquerading.
sendPGPMail.cgi is a small CGI script for sending an encrypted PGP email message to a predefined receiver from an HTTPS secured Web page. The typical use of this script is to provide the users of a secure Web site the possibility to send a secure email to a predefined employee of a company. The CGI script gets its input from an HTML form and passes it on to gpg. The message and its attachments are encrypted using the PGP public key of the predefined receiver.