Well, IMAP is an alternative solution to mail delivery. It's sort of a cousin to POP. The big difference in this case is that it keeps all of the mail on the server and your client manipulates the data on the server rather than downloading the messages and manipulating it there. That means that all clients see the exact same set of messages.

The problem with this is that you need an IMAP server that you can connect to, if not all of the time, then a decent amount of the time. So your first question is, is there a computer I have control of on the Internet that I can run a server on?