Considering the following scenario in a Microsoft Exchange Server 2013 environment:
A database availability group (DAG) contains at least two Exchange servers together with an active or passive mailbox database deployment.
Exchange servers belong to different MonitoringGroups.
In this scenario, when you failover the databases from Exchange server A to other Exchange servers, for example, Exchange server B, and then restart health monitoring service on Exchange server A, you find that a new health mailbox is created. This happens every time when the Exchange Health Manager Service (MSExchangeHMHost.exe) is restarted.
This issue occurs because unused health monitoring mailbox isn't clean up appropriately.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.