I have recently installed a second Exchange 2007 SP1 CAS, HUB and MB server (Server B) in a remote AD site from the first Exchange 2007 SP1 CAS, HUB and MB server (Server A). I have configured a second Internet Send Connector for Server B. Receive Connectors on both servers have the same settings.
Sending mail to and from the Internet from either server works as well as Internally appears to work although messages from mailboxes on Server B to mailboxes on Server A end up in Server B's queue for Next Hop Site A, Delivery Type SMTP Relay to Remote Active Directory Site. Last Error is 451 4.4.0 Primary Target IP address responded with: "421 4.4.2 Connection dropped." Attempted to failover to alternate host, but that did not succeed. Either there are no alternate hosts or delivery failed to all alternate hosts."
The reason I say appears to work is because my test messages from a mailbox on Server B to a mailbox on Server A show up in mailbox A's inbox but also ends up in Server B's queue as mentioned above. The messages in the queue stay there, giving Delivery Delayed messages to the Sender and then eventually fail and an NDR message with the following get send to Sender on Server B #550 4.4.7 QUEUE.Expired; message expired ##.
No errors are showing the App log on either server.
Mail Flow Troubleshooter run on Server B gives the error that SMTP ports 25 and 587 are not responding and gives the message "It appears that the SMTP service and SMTP instance(s) on server FRG-RNO-EX01 are started but the port did not respond. Check if there are any network errors or hung services." Also gives "Error submitting mail." A restart of Server B makes no difference.
I tested via telnet from Server B to Server B and was able to connect and send a test message successfully. Did same test from Server A to Server B which was also successful so it appears that SMTP is working fine.