After starting an Exchange 2019 test environment, I noticed that several Exchange services would not start correctly. This happened on multiple Exchange 2019 servers. Sometimes, a reboot resolved it; sometimes, it went from all services running to several services not willing to start.

This particular test environment had four Exchange 2019 servers and three Windows 2022/2025 Domain Controllers in one Active Directory site.

On one Domain Controller I found several EventID 4 (Security-Kerberos) in the System Eventlog:

The Kerberos client received a KRB_AP_ERR_MODIFIED error from the server dc01$. The target name used was P365\DC01$. This indicates that the target server failed to decrypt the ticket provided by the client. This can occur when the target server principal name (SPN) is registered on an account other than the account the target service is using. Ensure that the target SPN is only registered on the account used by the server. This error can also happen if the target service account password is different than what is configured on the Kerberos Key Distribution Center for that target service. Ensure that the service on the server and the KDC are both configured to use the same password. If the server name is not fully qualified, and the target domain (P365LABS.NL) is different from the client domain (P365LABS.NL), check if there are identically named server accounts in these two domains, or use the fully-qualified name to identify the server.

Obviously, there’s a mismatch in system passwords. To resolve this, I used the following command:

netdom resetpwd /s:dc01 /ud:domain\administrator /pd:<domain admin password>

Reboot the Domain Controller, reboot the erratic Exchange server and everything is working fine again.