Wants to share one interesting case.
Customer had 4 DC’s, two of them were on win2k8 and two of them on win2k12.
When they turning off two old DC’s – Exchange is dying. Exchange services are up, you can’t even stop them, and almost everything isn’t working from Exchange side (ECP, OWA, Outlook and so on).
The interesting thing is that Exchange see available DC’s and successfully switching between them.
Issue was solved by editing Microsoft.Exchange.Directory.TopologyService.exe.config (Bin folder):
MinSuitableServer = “1” (by default value is missing on CU11/12)
MinPercentageOfHealthyDC = “10” (by default value is 50)