Microsoft Exchange Server problem?

I am using Microsoft Exchange Server 6.5 . We are hosting our own email. About a week ago, one of the employees here said he could not receive outside mail. He could send mail, and receive mail delivered within the company, but he could not reeive mail from an outside source. I did a test by sending him an email from a gmail account, and it automatically bounced back.

Then, on Thursday or Friday of last week, another employee complained about the same problem!

Can anyone think of anything that might be causing this? Any suggestions?

Thanks!

Microsoft Exchange Server problem?antispam

Maybe there is a filter or blocking feature that is turned on? Look at the bounceback email, see if it has any clues.

Microsoft Exchange Server problem?avast

Another mind reading task.

At least post the bounced back question as this contain clues to your problem.