Problem with Outlook 2003 with no-existing recipient

Hello to everyone!
I am having a problem in a pc which is member of the domain (Windows Server 2003) where i work. There was an email form which was sent always with Cc to a recipient who used to work here. The email account now has been removed but whenever a mail is sent to anybody it returns Delivery Notification about the deleted account. I ve checked the cc,bcc fields and they are blank but is still does that. What could be the problem?

Thanks in advance,Dimitris.