The September update KB445127 for Windows Server 2016 from 20.09.2018 causes problems on domain controllers in connection with the Exchange GAL (Global Address List). After the update has been installed on Windows Server 2016 Domain Controllers, Outlook clients can no longer access the Global Address List:
I was also able to reproduce this problem, as soon as there are more than 18 recipients in an address list, Outlook can no longer display the address list.
The following error can be found in the event log on the Exchange Server:
EventID:5004
Source: MSExchangeIS
Microsoft Exchange Information Store service has encountered a transient error while reading information from Active Directory. Details:
Microsoft.Exchange.Server.Storage.DirectoryServices.DirectoryTransientErrorException: ErrorCode: AdUnavailable, LID: 52664 – Unable to retrieve mailbox information for mailbox with guid 04c826d7-adce-44d1-8d44-8e50ccbb07c3 —> Microsoft.Exchange.Data.Directory.ADTransientException: Cannot find Template Tenant.
I cannot say for sure whether the above error message is directly related to KB4457127, at least the event did not occur before I installed the update:
So far I have not found a solution other than uninstalling the update from the domain controllers:
2018-09 Cumulative Update for Windows Server 2016 for x64-based Systems (KB4457127)
I have only uninstalled the update from the domain controllers, the update does not seem to cause any problems on the Exchange servers. After uninstalling KB4457127, the GAL can be opened again.
As a precaution, the address lists should be updated manually once if the environment allows this:
Get-AddressList | Update-AddressList Get-GlobalAddressList | Update-GlobalAddressList Get-OfflineAddressBook | Update-OfflineAddressBook
Many thanks to Michael for pointing out this problem.