On Apr 18, 2008, at 5:57 PM, Joe Allesi -X (joallesi - Coyote Creek
Consulting at Cisco) wrote:

I have referred to the wiki and the RFC, but I still can't find the exact answer I'm looking for. From what I know, Dovecot uses the IMAP standard of 32 bit integers to uniquely identify messages.

After a message is deleted from the mbox, can this UID ever be
reissued to a new message or is that UID retired? What about after the 2
billion limit is reached?

The limit is 4 billion. There is code that if the UIDs reach that
high, a new UIDVALIDITY value is given (to invalidate client caches)
and all UIDs are renumbered to start from 1, but apparently that code
doesn't work.