I have a pretty simple configuration with 2 Exchange 2010 servers (each at Rollup 6 SP1 running under Windows 2008 R2 in a single forest/domain) in a DAG configuration. They're in different subnets with the primary server located in headquarters connected to the Internet and the secondary server in a branch office just used as a passive backup. Before applying MS patches this weekend to the passive server, everything was working fine. However after the patches, now whenever any mail reaches my primary server (on which all mailboxes are defined), the mail for some reason is being routed to the passive server and just sitting in the queue and going nowhere. I can fix the problem by merely turning down the Exchange services on the passive server and everything works again. What is possibly wrong and where do I go to troubleshoot this?
I've turned on logging and have looked through the logs but haven't seen anything that says there's a problem. I ran two tests for sending outbound mail:
. Outlook - mail left my mailbox and shows up in the passive server queue
. test-mailflow cmdlet from the active mail server which comes back with TestMailFlowResult: *Failure*
Again, after turning down the Exchange services on the secondary/passive server, mail goes out successfully on both tests.
I checked my Autodiscover under Outlook and it shows me connected to my primary server (I thought somehow I was being directed to the passive server but that isn't the case).
The only other change I am aware of from this weekend is a change in the network architecture. The passive server was in a subnet connected via a T1 circuit back to headquarters but now it's connected via a VPN back to headquarters. I don't think that should have anything to do with it.
Thanks for any assistance!!!