Thanks in advance.
We are in a transition from Exchange 2003 to 2010.
The 2003 servers consist of a clustered backend for mailboxes, one front-end server, and one bridgehead server.
Installed two 2010 CAS/HUB servers using microsoft network load balancing.
The first CAS/HUB installed the routing group connector. There are no problems with mailflow on that server (EX2010HUB01) to 2003 bridgehead (EX2003BH). We then added a second CAS/HUB server (EX2010HUB02) and mail is unable to flow from that server to the 2003 bridgehead.
We added the second server to the routing group connector by running the following:
Set-RoutingGroupConnector "EX2010HUB01-EX2003BH" -SourceTransportServers EX2010HUB01,EX2010HUB02 -TargetTransportServers EX2003BH
Set-RoutingGroupConnector "EX2003BH-HER1AAMEX11" -SourceTransportServers EX2003BH -TargetTransportServers EX2010HUB01,EX2010HUB02
The following error message is displayed in Queue Viewer
451 4.4.0 Primary target IP address responded with: "451 5.7.3 Cannot achieve Exchange Server authentication." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.
On EX2003BH, we've restarted the virtual SMTP server and confirmed that Integrated Windows Authentication is selected.