I have an exchange server2003 installed in my company. one of the users has outlook 2003 with email pop3 account configured, he was receiving and sending emails normally. suddenly he became unable to send, he receives emails normally but when he send an email it leaves outbox and sit on sent emails normally but it does not reach its destination even locally. I tracked his sent emails from exchange server it gives the following error " Advanced queue failed to deliver message". If I configure his email on other computer it works normally. Note that if he replied and email it reach destination but if he sends a new message it does not reach.
Can it be a virus?? the computer has AVG antivirus network edition with latest updates!
any ideas or solutions because I do not want to format the PC because all other applications are working properly??