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Authentication issues after upgrading to 2019/CU15
After upgrading to Exchange Server 2019 CU15, we started having many authentication issues. They appear in many forms. Executing a get powershell command on any virtual directory will fail for the remote system (I currently have 2 servers configured). It will log in the event viewer a DCOM 10028 error:
DCOM was unable to communicate with the computer (other system FQDN name) using any of the configured protocols; requested by PID 570 (c:\windows\system32\inetsrv\w3wp.exe), while activating CLSID {2B72133B-3F5B-4602-8952-803546CE3344}.
It is intermittent in nature. At first, I thought executing the Reset-ComputerMachinePassword would solve the issue, but it does not always work. We have one Windows 2025 DC in our infrastructure as we have seen some domain trust issues that have been a result of the 2025 DC. Microsoft recommends running this for those client systems. But those systems usually had an event logged in the DC indicating the need for resetting this password. This is not appearing for the Exchange servers.
When the get command fails, other issues such as Outlook clients not authenticating occur as well. The Outlook clients continuously prompt for credentials without accepting them, even though correct values have been entered. However, when the get command succeeds, so does Outlook.
Anyone experiencing this as well?
I have the fix. I wanted to wait a few days to make sure it worked before posting it here. Setting the policy “Network security: LAN Manager authentication level” to “Send NTLMv2 response only" on all Exchange servers appears to have fixed it. It did not appear to fix it when I had a combination of CU14 and CU15 servers. I had to upgrade all to CU15 for this to work.
I have the fix. I wanted to wait a few days to make sure it worked before posting it here. Setting the policy “Network security: LAN Manager authentication level” to “Send NTLMv2 response only" on all Exchange servers appears to have fixed it. It did not appear to fix it when I had a combination of CU14 and CU15 servers. I had to upgrade all to CU15 for this to work.
Hi there,
never saw this.
You can try to do this:
https://techcommunity.microsoft.com/discussions/windowsserver/dcom-was-unable-to-communicate-with-the-computer/1760463
BR Schnittlauch
