I have a domain set up on my server and set his MX records to a different IP
as requested by the domain user.

His mail works fine except for some reason no other domains on the server can email him?

Why can he not receive mail from anybody on the server but he can from anywhere else?

You can email anybody@domain.com from outside my server but any domain on the server it is returned.

My noc facility replys that the email server is lazy and does not check MX records and sends to user on the server.

How can I correct this?

For starters, make sure you are not set to recieve mail for him in the e-mail server, by removing any references to his domain.

Aside from that, I don't know.

Thanks I believe that does it. Problem was I had not removed it from the mail alias fields! Thanks again.