Symptoms
The Get-CalendarDiagnosticLog cmdlet gets proxied without checking if the destination is on a local forest or resource forest in Microsoft Exchange Server 2019 or Exchange Server 2016.
Resolution
To fix this issue, install one of the following updates:
For Exchange Server 2019, install the Cumulative Update 4 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.
For Exchange Server 2016, install the Cumulative Update 15 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.
References
Learn about the terminology that Microsoft uses to describe software updates.