Recreate arbitration mailboxes in Exchange Server

A couple of arbitration mailboxes are corrupt, and we like to make them healthy. It can also happen that the arbitration mailboxes objects are missing. That’s because they are removed from Active Directory Users and Computers (ADUC). The good news is that we can recreate the missing arbitration mailboxes. In this article, you will learn how to recreate arbitration mailboxes in Exchange Server.

Before you start to recreate missing arbitration mailboxes

Read the following articles about the arbitration mailboxes:

• Check Exchange arbitration mailboxes
• Move arbitration mailboxes in Exchange Server

Find the arbitration mailboxes in Exchange Server. Run Exchange Management Shell as administrator. Make use of the Get-Mailbox -Arbitration cmdlet. If you run the same cmdlet and you don’t see all the arbitration mailboxes, it means they are not in a good state. In our example, we have seven arbitration mailboxes.

We are running Exchange Server 2016 CU16. All of the arbitration mailboxes are configured in Exchange Server 2016 mailbox database DB01. You can see that we have seven arbitration mailboxes in the Exchange organization:

• 5x System mailboxes
• 1x Migration mailbox
• 1x Federation mailbox

In ADUC you will see the federation mailbox, migration mailbox and six system mailboxes. That’s a total of eight mailboxes. Why do we see eight mailboxes in total in ADUC and seven with PowerShell? The answer is that one of the system mailboxes is an audit mailbox.

The audit mailbox is the SystemMailbox{8cc370d3-822a-4ab8-a926-bb94bd0641a9}. You have to run the Get-Mailbox cmdlet with the -AuditLog switch to retrieve the mailbox.

Remove arbitration mailboxes

Go to ADUC. Right-click the mailboxes and click remove. We are going to remove the seven arbitration mailboxes. You will get a prompt if you are sure to delete the seven objects. Click Yes.

Run the cmdlet and check if the arbitration mailboxes are removed. There will be no results.

Remove audit mailbox

Let’s remove the audit mailbox too. It’s only one mailbox. A prompt will show up if you are sure to delete the object. Click on Yes

Run the cmdlet to check if the audit mailbox is removed.

In the next step, we are going to recreate the arbitration mailboxes and the audit mailbox.

Recreate arbitration mailboxes and audit mailbox

Find the Exchange Server ISO file in your files. If you don’t have it, download Exchange Server ISO from the Microsoft website. After it’s finished downloading, mount the ISO.

Find to which drive letter the ISO is mounted. In our example, it’s the I: drive.

Run Command Prompt as administrator and run the command I:\Setup.exe /IAcceptExchangeServerLicenseTerms /PrepareAD. This will recreate the missing arbitration mailboxes and the audit mailbox.

Start ADUC and make sure that you click the refresh button in the toolbar. If that doesn’t work, close and start ADUC. Verify that the PrepareAD setup created the arbitration mailboxes and audit mailbox in ADUC. A total of eight mailboxes.

Run both cmdlets to check if the arbitration mailboxes and audit mailbox show up. The results are empty, but why is that? That’s because we have to enable the mailboxes.

In the next step, we are going to enable the arbitration mailboxes. We will also enable the audit mailbox.

Enable arbitration mailboxes

Enable Microsoft Exchange Federation Mailbox

There are two cmdlets that we have to run.

Enable Microsoft Exchange Migration mailbox

Run the two cmdlets.

Enable Microsoft Exchange Approval Assistant mailbox

Run the cmdlet.

Enable Microsoft Exchange organization mailbox for OABs

Run the three cmdlets.

A warning is showing that you must invoke the cmdlet Update-OfflineAddressBook manually. Get the Offline Address Book and run an update.

Enable Microsoft Exchange Discovery system mailbox

Run two cmdlets to enable.

Enable arbitration mailbox Exchange 2016 CU8 and later (1)

Microsoft did not put any information regarding this arbitration mailbox at the time of writing. One cmdlet to enable.

Enable arbitration mailbox Exchange 2016 CU8 and later (2)

At the moment, Microsoft did not yet put any information regarding this arbitration mailbox. Run the seven cmdlets.

Enable audit mailbox

As of last, enable the audit mailbox.

Verify arbitration mailboxes

The mailboxes are placed in random mailbox databases. In our example, it’s placed in mailbox database DB01 and DB02. You can always move the arbitration mailboxes to another database.

Arbitration mailboxes are showing up and looking great.

Verify audit mailbox

Audit mailbox is showing up. Everything is looking fantastic.

Keep reading: Cannot delete mailbox database Exchange 2016 »

Conclusion

In this article, you learned how to recreate arbitration mailboxes in Exchange Server. Not only that, but you also learned that there is another system mailbox showing in Active Directory. It makes it confusing if you see a system mailbox in AD, but you can’t find it when running the Get-Mailbox -Arbitration switch. That’s because you have to run Get-Mailbox -AuditLog switch. After you recreate the mailboxes, don’t forget to enable them.

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