[rt-users] Postfix + RT3 Guide

[Bruce Segal]

To change the relaying restrictions on Exchange 55 take a look in the Internet Mail Service -> Properties -> Routing -> Routing Restrictions. You're probably not allowing any smtp connections to the exchange box. (guess)

Take a look here  ->  support.microsoft.com/?kbid=324059 

My setup for Exchange 2K doesn't really apply, but we only allow SMTP mail into our Exchange server from the postfix/rt box.   All other smtp connections would get the 550: relaying denied message.