New CMDlet: Clean-MailboxDatabase in Exchange 2013
Command is Update-StoreMailboxState

Examples:
This updates the mailbox state for a mailbox located on the mailbox database DB01
Update-StoreMailboxState -Database DB01 -Identity GUIDof DB
 
This updates the mailbox state for a mailbox located on the mailbox database DB01 with a GUID of 4a830e3f-fd07-4629-baa1-8bce16b85d44.
Update-StoreMailboxState -Database MDB01 -Identity 4a830e3f-fd07-4629-baa1-8bce16b85d44
 
This updates the mailbox state for all disconnected mailboxes on the mailbox database DB01.
Get-MailboxStatistics -Database DB01 | Where { $_.DisconnectReason -ne $null } | ForEach { Update-StoreMailboxState -Database
$_.Database -Identity $_.MailboxGuid -Confirm:$false }