From PackGy. I noticed that my Outbox was building with mail. When I'd shut down I'd get the message, "do you want to send mail in the Outbox?" It kept pointing to the same email as the culprit. I 'assumed' it would pass by a problem email and go on to the next one. It appears it does them one after another in sequence. If first one has a problem it stops. No attempt made on any other one. I know this because I finally just deleted the one it kept mentioning at... Then all the others were sent! Problem is gone! Hope this helps someone else.