XCON: Site Connector Not Usable Through a Firewall

According to the Microsoft Knowledge Base article 161931  (http://support.microsoft.com/kb/161931/EN-US/ ) , "XCON: Configuring MTA TCP/IP Port # for X.400 and RPC Listens," two Exchange Server computers in different sites can be configured to communicate through a firewall by setting the desired port numbers for RPC Listens. However, if the firewall filters incoming and outgoing ports, no mail is flowing and the event log shows the following 9322 error:

The calling Exchange Server MTA issues a RPC bind command that contains a TCP port number to be used in the reply, the bindback RPC command. When replying, the called MTA does not use this port number, and as the firewall is configured to let go through only this port number, the reply is never received by the calling MTA. The communication is not established and as a result no mail can be sent or received.

To resolve this problem, obtain the latest service pack for Exchange Server version 5.5. For more information, please see the following article in the Microsoft Knowledge Base:

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.5.