After you’ve installed the Exchange 2013 mailbox role a default database is mounted as well:

Next, create one of the future production databases on the same server:
To get a list of mailboxes on the original database, run ‘get-mailbox |ft name,alias,servername,database’ in PowerShell:
To move the mailboxes on the original database, run ‘get-mailbox | new-moverequest -targetdatabase database01’ in Powershell. Once you run this, check the move request by running “Get-MoveRequest” in PowerShell:
Once the move has completed, you can run another “get-mailbox |ft name,alias,servername,database” to verify the mailbox has moved:
Now that you’ve moved those mailboxes, go ahead and delete the original mailbox store. However when you attempt to delete the mailbox store, an error message pops up about some arbitration mailboxes that are on the database.
So how do you reveal these arbitration mailboxes and what are they for?
To read more about arbitration mailboxes, check out these links:
- http://technet.microsoft.com/en-us/library/gg588318.aspx
- http://technet.microsoft.com/en-us/library/dd297936.aspx
- http://blogs.technet.com/b/exchange/archive/2009/06/10/3407662.aspx
- http://blog.chrislehr.com/2009/10/exchange-2010-what-is-arbitration.htm
To reveal the arbitration mailboxes, run “get-mailboxdatabase | Get-Mailbox -Arbitration |ft name,alias,servername,database” in PowerShell.
To move these mailboxes, simply run “get-mailbox -arbitration | new-moverequest -targetdatabase database01” in PowerShell:
Verify that these moves have completed, run “get-mailbox -arbitration | new-moverequest -targetdatabase database01” in Powershell:
Once these moves have completed, you can now remove the database:
Then the default database is removed:
As is well documented in the blogs and support forums, Exchange 2010 has the same hidden mailboxes. We just need to be aware that these still exist in Exchange Server 2013.
Just remember that if you need to adjust your mailbox databases once more, these mailboxes will have to move again before you delete those mailboxes.