SMTP Help

[David Drury]

Greetings,
I'm installing a Postfix server to help protect an MS Exchange server, and 
its denying relaying. To test, I'm using a mail client (like enlightnement) 
to try and send e-mail to destination mail boxes on the exchange server via 
the Postfix relay. If that works is there any difference between that and a 
mail server talking to the relay ? 

If there is, what is a good way to test a mail server without having it  
live. 

Thanks 

 --
David Drury
Network Administrator
Peregrine Corporation
"He's mostly dead, Jim. Get Miracle Max"