I've used outlook and mozilla to manage several email accounts in the past, but now I like Yahoo! With Yahoo mail plus you can access pop accounts. So email from several of my domains gets sent to my Yahoo inbox. And its not just forwarded there. they show up as to
me@otherdomain.com and I can reply and it automatically sets the from field correctly. I also love the address-guard that you get with yahoo mail plus. it lets you create disposable email addresses to kill in case you start getting too much spam! Their spam filtering seems to work pretty well for me too! the only drawback to this is you need to be online to read old email, but with a cable modem its not a problem for me!