Or, if you lived in Eastern Europe, The Bat1[1] - and it is still actively supported!
I switched to Opera Mail because it was convenient to have the browser and email client in one software (which is also freeware), but that went with the Chropera move.
The Bat was quite nice! I used it for a while but finally switched to the Japanese client "Becky Mail", ugly but quite functional. I still have some backups in a zip drive I should restore...
http://web.archive.org/web/19980212160741/http://www.email-c...
edit: fix link