Eudora PRO definately does. The Internet Mail that comes with Microsoft's
IExplorer does as well. ccMAIL has really good rules-based filtering (I
think the "mobile" version is useable on the net(?)), the later versions of
Pegasus email also sort. I use the Internet Mail that comes with MS
Explorer release 3 (I think they measure these releases in the thousands
these days!) - like the browser, it is free but you need a PC running
Win95 or WinNT. (http://www.microsoft.com/IE).
ftp://papa.indstate.edu/winsock-l & follow the directories to find your
platform & "Mail" directory.