Since e-mail clients and spam filtering options are always of interest to migrators, it's worth mentioning that there is a Eudora 6.0 beta available now (Mac only, interestingly) that has built-in spam filtering. I've been using it for several days and am very impressed.

Leaving aside minor new stuff like the mysterious "Content Concentrator," the big deal is spam filtering. It seems to incorporate some combination of header-scanning and Bayesian keyword filtering. (If you have inside info on the specifics, please post!) It works quite well out of the box with no explicit training. Results for my first three days and 1200 messages are very good -- it's catching 97.5% of my spam. Giving it feedback on what's spam and what isn't is easy (you can assign the Junk/Not Junk commands to function keys). Filtering is virtually instantaneous. Old stuff in the "Junk" mailbox can be automatically cleaned out after X days. Plus, they fixed the crazy memory leaks I was seeing with 5.2. No detectable stability problems. This is the most hassle-free and effective spam filtering I have ever used. Just say No to endlessly tweaking spam filter rules. Discuss