CiviMailProcessor should help you find the message it gets stuck on

Sometimes CiviMailProcessor gets stuck on a message and just quits processing. The next time it runs, that message is at the top of the queue, so it just quits again. At some point we should probably have it randomize the order it processes things in or have it detect these repeat failures and skip the message at the top of the queue on the next run. And obviously we should figure out why it's getting stuck and fix that too when it happens.

But for now, I can't find the message it's getting stuck on because CiviMail doesn't give me any clues as to which it might be. I get an ID from the IMAP server, but I would need a subject line and maybe a sender e-mail address to really track it down and eliminate it from the queue.