User homed on Member Exchange 2K3 in Site-B sends message to an internet recipient, message goes to Master server in Site-A and is not delivered to recipient, an NDR is generated but it never makes it back to user in Site-Bs mailbox, even though Message Tracking says it did. All other email between both sites is working fine, and to and from the internet. Both servers are part of same domain, different sites with domain controllers at both sites AD DNS at both sites running Exchange 2K3 SP1, on Windows 2K3 servers in an 2K3 AD domain. This is my first post. Let me know if I need to supply more information. Thank you.