Symptoms
When you run the Set-AcceptedDomain cmdlet to modify existing accepted domains in your organization in Microsoft Exchange Server 2016, you may find the MatchSubdomains parameter isn't available.
Cause
This issue occurs because the MatchSubdomains flag isn't enabled for Exchange Server 2016.
Resolution
For Exchange Server 2016, install Cumulative Update 9 or a later cumulative update for Exchange Server 2016.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology that Microsoft uses to describe software updates.
