Unhealthy state of Exchange servers when monitoring mailboxes are deleted

• Applies to:

  Exchange Server 2019, Exchange Server 2016, Exchange Server 2013

Symptoms

In Microsoft Exchange Server 2019, 2016, or 2013, you deploy multiple servers that are named, for example, EXCH, EXCH-02, and so on. In this situation, you notice that the monitoring mailboxes and associated Active Directory accounts for EXCH-02 are deleted every hour, even after you re-create them. Additionally, Get-ServerHealth shows many health sets in an Unhealthy state because of the missing monitoring mailboxes.

Cause

This issue occurs because the monitoring mailboxes are incorrectly deleted by the MonitoringMailboxCleaner process. This process runs every hour on every server that is running Exchange Server. It removes monitoring mailboxes that are no longer needed by that server. To build the list of mailboxes that are to be checked, the process examines the DisplayName value of the accounts by using a pattern match for the HealthMailbox-SERVERNAME- string. Then, it evaluates each item on the list to determine whether that item should be deleted.

In this scenario, when the process runs on server EXCH, the list includes all mailboxes that have a DisplayName that matches the HealthMailbox-EXCH- string. This includes the mailboxes for both EXCH and EXCH-02. The process sees the EXCH-02 mailboxes as invalid, and then deletes them.

This behavior can be observed in the Active Monitoring trace logs that are located in <ExchangeInstallDir>\Logging\Monitoring\Monitoring\MSExchangeHMWorker\ActiveMonitoringTraceLogs.

Resolution

To fix this issue, use a different naming convention that does't include hyphens for the servers that are running Exchange Server.

If the servers have already been set up in this manner, you can prevent the issue from occurring by selecting the Protect object from accidental deletion option in Active Directory Users and Computers. To do this, follow these steps:

1. Open Active Directory Users and Computers.
2. Select View, and verify that Advanced Features is selected.
3. Expand the domain, expand Microsoft Exchange System Objects, and then select Monitoring Mailboxes.
4. Double-click the first HealthMailbox<GUID> object.
5. Select the Object tab.
6. Select the Protect object from accidental deletion option, and then select OK.
7. Repeat steps 1–6 for each HealthMailbox<GUID> object in the Monitoring Mailboxes container.