Anytime a specific user sends an email too any other person, that person receives two copies of the email. What conditions could allow this to happen?
3 Answers
This can happen if there are two copies of the OUTLOOK.EXE process running on the machine. Ending one of the processes will stop duplicate mail from being sent out.
Sounds like you already solved this but for future occurrences, it might also help to see headers.
Outlook profiles crap out sometimes and give wacky results. Just a general Outlook/Exchange troubleshooting method. When having issues troubleshoot them in Outlook, try to reproduce them in OWA.