Qmail-Scanner, (also known as scan4virus) is an addon that enables a Qmail Email server to scan all gatewayed Email for certain characteristics. It is typically used for its anti-virus protection functions, in which case it is used in conjunction with commercial virus scanners. but also enables a site to react to Email (at a server/site level) that contains specific strings in particular headers, or particular attachment filenames or types (e.g. *.VBS attachments). It also can be used as an archiving tool for auditing or backup purposes. Qmail-Scanner is integrated into the mail server at a lower level than some other Unix-based virus scanners, resulting in better performance. It is capable of scanning not only locally sent/received Email, but also Email that crosses the server in a relay capacity. It also has SpamAssassin support.
whatsnewfm is a filter for the daily freshmeat newsletter. It shows only news items that you haven't seen before (so you don't have to read about every update of applications that you aren't interested in). You can also set up a list of "interesting" applications where you want to be informed of every update.
MIMEDefang is a flexible MIME email scanner designed to do all kinds of email processing, including anti-virus scanning, anti-spam scanning, replacing parts of messages with URLs, adding boilerplate disclaimers, and so on. It can alter or delete various parts of a MIME message according to a Perl-based policy filter. It can also bounce messages with unacceptable attachments and modify SMTP response codes on the fly. It works with the Sendmail 8.11 and newer "Milter" API, which makes it more flexible and efficient than procmail-based approaches.