I tried out the Mozilla Thunderbird mail client yesterday. They just released version 0.4 a few days ago. It mostly works on Windows XP but hangs trying to copy messages to the Sent folder. I think I’ll switch to it when they get that problem fixed. I’m currently using a crusty old MIT-provided version of Eudora, which feels pretty clunky compared to other clients I’ve used (e.g. Apple iMail, which doesn’t run on my PCs).