Forum Discussion
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 ...
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.
Unfortunately, this problem has appeared again. I'm trying to figure out the solution. I don't know if it related to recent updates (Aug. 2025) or something else.