[dlk9s]

I called Comcast back and the rep confirmed what ghostbeef said. They only allow outgoing e-mail through their SMTP server (although that still doesn't explain why incoming wasn't working, either).

We went through some steps to try to fix it, but it still didn't work. He then told me Outlook Express should work and that I should set my incoming to POP3, using my Exchange server address and outgoing to SMTP (Comcast). I don't have Outlook Express on my work computer right now, so I just tried it on my other computer and, what do you know, it worked. All my e-mails downloaded and test e-mails back and forth went through.

So, I guess I'll be using Outlook Express, which I suppose I don't mind. As long as I have all my old sent and received e-mails, I'm happy.

Thanks for everyone's help!