Smail is a Mail Transport Agent. Its job is to accept mail messages from sources on the local machine, or from remote hosts, and deliver those messages to the appropriate destinations, be they to remote hosts or to files or programs on the local machine. Smail is designed to be mostly compatible with sendmail but uses a much simpler configuration scheme.
Rumble is a mail server suite for SMTP (ESMTPSA), HTTP, POP3, and IMAP4v1 with an extensive C/C++ and Lua API for scripting. It comes with support for SSL/TLS, SQLite, and MySQL and has a Web-based administration and Web mail feature. Additional included modules feature greylisting, DNS blacklisting, SpamAssassin support, and dynamic performance scaling as well as a multithreaded structure that allows for clustering of multiple servers for one or all domains. With the Lua API you can create your own new server mailing lists, CRM software, e-marketing, and other extensions within minutes.
SPF is a new strategy for preventing junk mail. The present SMTP standard for email allows anyone to forge anyone else's email address. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it. libspf2 is a complete and robust implementation of SPF which provides support for many MTAs. Support for new MTAs is in progress.
libsrs2 is the next generation SRS library. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it. When a message is forwarded, the sender address must be rewritten to comply with SPF policy. The Sender Rewriting Scheme, or SRS, provides a standard for this rewriting that is not vulnerable to attacks by spammers, is easy to parse by common mail filters, and handles multiple hops neatly and safely.
Spey is an SMTP proxy that sits between your existing mail server and the outside world, blocking spam using a greylisting technique. It is simple, lightweight, easy to install and configure, requires minimal changes to your existing mail server, is completely independent of which mail server you're using, and extremely effective. The author's spam intake has dropped from over a hundred messages a day to about 5. It uses the Sqlite database library as a backend.
FetchYahoo is a Perl script that downloads mail from a Yahoo! account to a local mail spool. It is meant to replace fetchmail for people using Yahoo! mail since Yahoo!'s POP service is no longer free. It downloads messages to a local mail spool, including all parts and attachments. It then deletes messages unless requested not to. It can also optionally forward messages to a specified email address and repeat with a given interval.
Tellmatic is a tool to manage and create newsletters for personalized mailing or mass mailing. Addresses and newsletters are stored in groups to handle different user groups and thousands of addresses at a time. SMTP is used for sending the newsletter to your subscribers to make sure you get all error and bounce messages. Bounces can be handled automagically via a small bounce-management module with POP3 access. It also has a small form-editor and statistics. You can import and export your addresses in CSV format.
SubEthaSMTP is an easy to understand Java library that provides a receptive SMTP server component. By plugging this component into your Java application, you can easily receive SMTP mail using a simple abstract Java interface. Also included is a small sub-project called Wiser, an easy to use incoming mail testing framework.