another email problem

[G7pro]

I have an email address that I am trying to connect to. It is a remote address not set up on our server. I am able to reply to his emails fine when he sends me one. But if I try to generate a new email to the same address it always fails. The only difference I see in the log other than that one fails, is that when I reply to his email it shows

"relay=mx.central.cox.net"

where as when I create a new email that fails it says

"relay=none"

any ideas on where I need to look for a solution to this? Let me know if you need other information.