Grinch is a small Perl script which can be used to check whether a given address is an open mail relay host. It can operate as a daemon, and speaks the tcp_map protocol implemented in Postfix when it runs as a daemon. It can also be used in arbitrary shell script environments where the hostname is read from stdin and the error code is written to stdout, which allows it to be used with qmail and other MTAs.
spfmilter is a milter (sendmail mail filter) which implements the Sender Policy Framework (SPF). SPF is a strategy for preventing junk mail. The 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.
fakehermes is a small, lightweight fake SMTP server. It's useful as a way to avoid spam by configuring your domains to point their secondary SMTP server to a fakehermes server. It will log not only the email messages involved, but also how they are trying to send email and whether they should be considered spam or not. This information can be used to "profile" the spammers that send you spam and can allow you to configure or tune other spam filters. It supports SPF and RBL checking.
libSmtpThread is a multi-threaded C++ library for sending mail via SMTP. The library provides a connection pool that initializes a set of threaded SMTP connections. Emails can be pushed into the pool, which accepts all mail and delivers them to a free connection. The delivery to the SMTP server is processed in a separate thread, so you don't have to wait for mail to be accepted. It has been successfully tested with Postfix.
JeguePanel is a panel to provide easy management of GNU/Linux servers. It makes services configuration (email and samba) much more easy and efficient, and handles user and permissions management. It's integrated with monitoring tools and a lot of control programs like anti-virus, anti-spam, reports, etc. It has English, Portuguese, and Spanish translations. It can use OpenLDAP, PostgreSQL, or MySQL as a backend, and has full integration with Active Directory. It will show different interfaces to users based on permission levels.
elspy is a layer of glue code that enables you to write Python code to scan email messages at SMTP-time with the Exim MTA (mail transport agent). It also includes a small Python library with common mail-scanning tools, including an interface to SpamAssassin and a simple-but-effective virus detector.
PMilter implements Sendmail's "milter" mail filtering protocol in Perl, allowing scripts direct access to the SMTP transaction in progress, rather than filtering later. It can function as a drop-in replacement for Sendmail::Milter, though PMilter does not require threads or the "libmilter" API to be available.
Swift is a library for sending email messages from PHP Web sites and applications. It does not rely on PHP's native mail() function (which is known for using high server resources when sending multiple email messages). Instead, it communicates directly with an SMTP server or an MTA binary to send mail quickly and efficiently. It features custom headers, multiple encoding options, TLS support, embedded images, building and sending multipart messages, fast Cc and Bcc handling, batching messages with or without multiple "To"s, support for multiple attachments, setting message priorities, requesting read receipts, pluggable SMTP Authentication (LOGIN, PLAIN, MD5-CRAM, POP Before SMTP), anti-flooding support (reconnect every X email messages ), secure Socket Layer connections (SSL), and loadable plugin support with event handling features.