Symptoms
In a Microsoft Exchange Server 2019 or Exchange Server 2016 DAG setup, restarting health manager service creates new health monitoring mailboxes for each database on the Exchange server. You can ignore the duplicate mailboxes, but the duplicate mailboxes keep piling up.
Resolution
To fix this issue, install one of the following updates:
For Exchange Server 2019, install the Cumulative Update 9 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.
For Exchange Server 2016, install the Cumulative Update 20 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.