Email Bounce Backs and Undeliverable

All,
I have a peculiar situation happening with one of my users who has an email box on our Exchange 2000 server. This particular individual worked for our company a couple of years ago and left. His email account was deleted along with his actual mailbox. I then created him a new Exchange account through Active Directory. Other employees within the organization have reported getting email bounce backs or delayed delivery notifications when sending email to this particular individual. This does not appear to be happening with anyone else in the organization. Does anyone have any ideas on what could be happening here or what things I could check to correct this problem? Thanks for your feedback.