I have a user that keeps receiving "undeliverable" or "mailbox does not exist" auto reply messages regarding emails she has not sent. It appears to me that her machine has a virus and is sending out mass emails from her account. Her computer has been checked thoroughly for a virus, and appears to be clean though. We're using Exchange 2003, and Ironmail as our filter. These outbound messages are being logged in Ironmail, so it appears that they are being generated and sent internally. Any ideas on how to track this down?