Thunderbird Email Client
Thunderbird Mozilla's next generation FREE e-mail client. Thunderbird makes emailing safer, faster, and easier than ever before with the industry's best implementations of features such as intelligent spam filters, a built-in spell checker, extension support, and much more.

Eudora Email Client
A rock solid email client. If you choose "light mode" during the install it is totally FREE. The paid version has a great SPAM filter.

Pegasus Email Client
Pegasus Mail is a FREE, standards-based electronic mail client suitable for use by single or multiple users on single computers or on local area networks. A proven product, it has served millions of users since it was released in 1990. It is extremely feature-rich and powerful, yet remains small and fast.

SpamBayes Spam Filter
SpamBayes is a tool used to segregate unwanted mail (spam) from the mail you want (ham). It comes in various flavors. The Outlook plugin is the one I think many of you would be interested in. The plugin does NOT work with Outlook Express.

SPAM Fighter
SPAMfighter Standard is a FREE tool for Outlook and Outlook Express that automatically and efficiently filters spam.