A POP server’s Update State is used to actually delete messages from a mailbox that have been marked for deletion during the Transaction State. This state is entered only if messages have been marked for deletion and a QUIT command is received during the Transaction State.

If messages marked for deletion are reset by the RSET command, a following QUIT will not cause the server to enter the Update State.

After any messages awaiting deletion have been deleted, a server clears the lock on the mailbox being operated on and ends the session. The corresponding client may have already closed the network socket while these actions are being carried out.