Yes, I know that trick. It's good, but IMAP defeats it. An IMAP server must
declare the existence of messages in strictly ascending order, so if
there's an outage and the servers have added messages (and avoided UID
conflicts) they may still have a protocol conflict. They can't just tell
clients "I told you about 10000003 a while ago, well, now 10000002 also
exists".
The foo bar I mentioned about \recent and uidvalidity solve that ordering
problem.
Arnt