The best multiple webmail client I have found so far is ePrompter... First, you should be informed that it downloads messages but not attachments. If you use it and want to download an attachment, you have to log in and get it. Similarly, you can send mail but not with attachments. Check it out at
http://www.eprompter.com/ - from this site, it is noted that supported email services include AIM, AOL, Gmail, Hotmail, Yahoo, POP3, Earthlink, Excite, Juno, Lycos, Mail.com, Mindspring, MSN, MyWay, Netscape, Rediffmail, SBC Yahoo, USA.net
Arun