[Dovecot] Message UID Question

[Joe Allesi -X (joallesi - Coyote Creek Consulting at Cisco)]

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?

Thanks!