A user reports to me that she got an Undeliverable message ("Your message did not reach some or all of the intended recipients.") from the System Administrator. She didn't send any message to the Person1 at all. And that name is not in the domain users list. Any clue for solving this puzzle???
"The following recipient(s) could not be reached:
Person1 on 06/06/2013 3:25 PM
The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address."