In response to my comment about downloading bounced spam replies over dial-up, Hanan Cohen pointed me to a piece he wrote,
IMAP - the best-kept secret in electronic messaging, in response to a post Doc made a while back. I'll have to reconsider that. However, I have used IMAP before, and I wasn't a big fan. I don't remember exactly what the problem was—it may have been specific to the implementation on our email server (IMAIL)—but I found it a bit cumbersome.