We recently changed to a 2008R2 domain & forest functional level and after testing and noticing no issues within the first hour no issues, then the server stopped processing all emails and flooded the system log with error:
Error Event ID#1
Unhanded Exception "Could not find any available Global Catalog in forest domain.xxxxx.com."
Approximately 11 hour or so after our domain functional level change and these updates we found out the hard way emails coming to a stop. We have 3 exchange servers, 2 physical and 1 VM. Only 1 had the issue (which carries all 4 roles, and is the main server).
To fix the issue, I restart the AD Topology service, which restarts a bunch of exchange services, and the server finds the GC and operates normally again.
6 DC's across 3 sites in MPLS environment of which 2 are local to the exchange box (on the same rack). Now every 10 hours or so the event logs show event id and it shows that it attempts its routine 15 min interval topology checks and out of nowhere it cant find any GC's? Its at this point that we go down hard.
We have checked that all DC's are setup as GC, check to make sure under ADSS GC is shown and DNS does have GC listed too. When this issue occurs we can ping, nslookup and UNC to all the domain controllers and vice versa from the exchange box without any issue.
Any thoughts? It seems to have been related to the 2008R2 schema upgrade from 2003 as we never had this issue prior.