Microsoft, Opera, and PBW

[Sivran]

And Thunderbird is safer than Oh No Virus Installer.

However I'd say Pegasus Mail is the best free Windows mail client.

Mozilla and Firefox are great with Tabbrowser Extensions and Mousegestures (http://extensionroom.mozdev.org) and the Firebird-only Flash Click-to-Play is also very nice.

One thing to consider when trying Firefox however: the newly-named Version 0.8 is much different from Firebird 0.7 and you may find you like the older one better. They changed a lot with 0.8 and it needs time to mature.

Mozilla proper, of course, hasn't changed much in look and feel in a long time and 1.6 is yet another good Version. They've more than made up for the disaster of 1.4