[e12e]

So, the "solution" is to have your users set up a .forward-filter that pings a web service on new mail? Then have a really simple status server that simply replies with number of new mails since last check (or something along those lines...) - and have your email client poll (and reset) that counter... would give a few false-positives, but probably be better than having to poll an actual (variety of) IMAP/POP3-servers.

(This obviously won't work for most end-users, sadly)