I've hacked into the authentication modules a bit, but haven't gone into the IMAP code itself, so I don't know specifics. I would imagine it would be relatively straightforward, though. When a user logs in, have the code attempt a Hotmail connection instead of verifying the password locally. Then, any command that would have accessed local files and folders instead sends the relevant queries to Hotmail connection, giving a temporary error if the connection hiccups and terminating the IMAP session if the connection disappears. A lot of this would depend on how closely the XML commands resemble IMAP commands. Hopefully somebody else will offer better help with the little details. Good luck!