Pygmy
- A GNOME mail client written in Python. Pygmy supports attachments and MIME messages, both in the message composer and in the message viewer.
- http://pygmy.sourceforge.net

maildrop - mail delivery agent with filtering
- Maildrop reads a mail message from standard input, then delivers the message to your mailbox. maildrop will optionally read instructions from a file, which describes how to filter incoming mail. Instructions can be provided having mail delivered to alte
- http://www.courier-mta.org/maildrop/

Fetchmail
- Fetchmail is a free, full-featured, robust, well-documented remote-mail retrieval and forwarding utility intended to be used over on-demand TCP/IP links (such as SLIP or PPP connections).
- http://fetchmail.berlios.de/

The Fetchmail FAQ
- Frequently asked questions about fetchmail.
- http://catb.org/~esr/fetchmail/fetchmail-FAQ.html

archivemail
- Python tool for detecting and compressing older e-mail messages.
- http://archivemail.sourceforge.net/

BSD Vacation V2
- RFP-compliant vacation mailer, designed to replace the standard Sendmail vacation program.
- http://www.weird.com/~woods/projects/BSD-vacation-v2.html

Vacation Auto-Reply (Unix)
- Simple instructions for one variant of the vacation(1) program on Unix. (This doesn't appear to be the most standard version, but the general instructions look relatively ok.)
- http://www.emailman.com/vacation/

Mailfilt, by Mike Fisk (Unix/Perl)
- Mailfilt is a procmail-like Perl application for filtering your mail. (Last updated sometime in 1995 ...)
- http://www.nmt.edu/~mfisk/style.cgi?unixtools/mailfilt.html