Exchange 2010 Mailbox server role installation create a default mailbox database which consist of System mailboxes and a Federated mailbox.
As we all know, in case if we decide to remove this Default mailbox database we need to move all mailbox to a different Database.

In one case while trying to move Federated mailbox I was getting error “Mailbox size 1.009 MB exceeds target quota 1 MB”

Though the destination Database had no limit defined.
Tried to move by defining limit on database, still of no use.
Tried to remove quota from Federated Mailbox, in this case I was greeted with error similar to “Cannot find the on DC01.domain.com” (I don’t remember the exact error)

So, to get out of this, use ADSIEdit, browse to “Users” container and find “CN=FederatedMail.xxxxx-xxx-xxxx-xxxx”.
Go to it’s properties and fine Attribute “mDBUseDefaults”
By default the value is set to “False”. (as shown below)
Change it to “True”

Now I was able to move Federated Mailbox to another DB.

As a precaution, after the move was complete I did set “mDBUseDefaults” value back to “False”