I think you have a lot of options for working with mail. One simple option that a friend turned me on to was using GMail (www.gmail.com) to fetch mail from my 3 different mail accounts. It's always available from multiple computers, and doesn't tie me into a stand-alone mail application (which I've always preferred up until trying this). And Google being a 3rd party company does a great job in supporting non-IE browsers. I personally use Firefox and it works great.

Another option would be to use Exchange and Outlook Web Access, which is also a web based solution. However OWA doesn't work quite as nicely with non-ActiveX browsers. I'm also not entirely certain that Exchange will pull through POP/IMAP from other mail servers. I know that it certainly supports it for mail delivered to a mail domain that it personally hosts, but I'm not sure about remote servers. Unless you are looking to have the mail forward to the Exchange server's domain.