A user has sent in an email, and for some reason, every 10 or 15 minutes, a new Service Call is created. No new email messages are being sent to Service Desk from this user. Exchange 20003's message tracking confirms that only one (1) message was sent to Service Desk. other users have been able to send requests without any issues since this problem has begun.
Thanks for you response. Unfortunately, it wasn't an autoresponse. I've just found that there was something wrong with our SMTP queue on the Exchange Server. It was looping some (not all) externally redirected messages. The problem was solved simply by clearing the SMTP queues.