Remove default mail database

Question

Dues to the size of my default mailbox database I created two new mail box databases and moved (using EMC) the existing user mailboxes from the default mailbox into the two new ones (half in each new database). That left me with the Discovery Search
Mailbox which I loved (using EMC) to one of the new databases. Am I now safe to remove the default database or is there something further that I need to do first? I read something about arbitration mailboxes but don't know what those are or if they are
already handled by moving my user mailboxes and the Discovery Search mailbox. When I run "Get-Mailbox -Database" against the default database it shows no objects. I think I'm ready to remove the default database but am nervous about doing that without
checking first.

Answer 1

Hi Don,
Hope you are doing well.
there is nothing wrong in removing your default database but there are few steps / precautionary measure that you need to take before you remove your default database and those are as follow.
Move Arbitration Mailboxes
Move Discovery Mailbox
Move User Mailboxes
Move Archive Mailboxes
If you miss out anything and if you try to remove the Default Database you might face a popup with an Error.
Microsoft Exchange Error
The mailbox database ‘Mailbox Database 0089743213′ cannot be deleted.
Mailbox Database 0089743213
Failed
Error:
This mailbox database contains one or more mailboxes, mailbox plans, archive mailboxes, or arbitration mailboxes. To get a list of all mailboxes in this database, run the command Get-Mailbox -Database <Database ID>. To get a list of all mailbox plans
in this database, run the command Get-MailboxPlan. To get a list of archive mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -Archive. To get a list of all arbitration mailboxes in this database, run the command Get-Mailbox
-Database <Database ID> -Arbitration. To disable a non-arbitration mailbox so that you can delete the mailbox database, run the command Disable-Mailbox <Mailbox ID>. To disable an archive mailbox so you can delete the mailbox database, run the
command Disable-Mailbox <Mailbox ID> -Archive. Arbitration mailboxes should be moved to another server; to do this, run the command New-MoveRequest <parameters>. If this is the last server in the organization, run the command Disable-Mailbox <Mailbox
ID> -Arbitration -DisableLastArbitrationMailboxAllowed to disable the arbitration mailbox. Mailbox plans should be moved to another server; to do this, run the command Set-MailboxPlan <MailboxPlan ID> -Database <Database ID>.
Get-Mailbox -Arbitration | NewMove-Request -TargetDatabase "xxxx" ==> This command will get all the arbitration mailboxes and move them to new database to which you want to move.
Get-Mailbox -Filter { RecipientTypeDetails -eq "DiscoveryMailbox" } | new-moverequest -targetdatabase xxxxxx ==> This command will move the discovery mailbox to your new databse.
You can move the user mailbox from Admin Center or EMS by using the following command.
New-moverequest -identity abc@xyz -targetdatabase "xxxx"
Once you are done with the move of all user, discovery and arbitration mailboxes, dismount the database for couple of days to see if there is still any impact on production (It will not have any impact but best practice is to dismount your database first
and then remove it after couple of days). If you don't have any issues with your production after dismounting the default database, remove it after 2-3 days. Thanks.
Regards, Riaz Javed Butt Consultant Microsoft Professional Services MCITP, MCITP (Exchange), MCSE: Messaging, MCITP Office 365