ok I am starting to set up for a major rollout for a client.
All servers will be Exchange 2003 on Windows 2003 server.
First server was setup just to get started, il1-2k3-04, smtp connector to relay any non-migrated mail back to the old ISP email system. Everything works fine.
I installed a frontend server in the DMZ, Set backend SMTP virtual server smart host to the front end. Moved bridge head for old isp relay to front end server.
All out going mail works great. Untill there untill we try to have mail routed from the front end to the back end, at which point we get a Diagnostic-Code: smtp;550 5.7.1 Unable to relay for email@example.com
P.S. Firewall is wide open between DMZ and internal for this address.