Something I just thought about doing optionally: Mark the message expunged using some non-standard flag and expunge it later (maybe in some nightly run). Don't show expunge-marked messages to clients, unless they haven't been notified that it's been expunged. Don't do the real expunging unless the flag was set less than hour ago. That should make it highly unlikely that anyone hasn't been notified of the EXPUNGE yet.
<snip> Maybe you could do something similiar.
This is an interesting idea, thank you. It is not useful to me though. That's because, within the domain of my IMAP server, I could do better and the real problem is that of messages being expunged by other (non-IMAP) mechanisms (as was mentioned by the Exchange folks).
Pete
