When mailboxes are moved from a Microsoft Exchange Server 2010 Service Pack 1 (SP1) database to any other database, Exchange doesn't fully delete the mailbox from the source database immediately upon completion of the move. Instead, the mailbox in the source mailbox database is switched to a soft-deleted state, which allows mailbox data to be accessed during a mailbox restore operation by using the new MailboxRestoreRequest cmdlet set. The soft-deleted mailboxes are retained in the source database until the deleted mailbox retention period expires.

A mailbox is marked as Disabled immediately after the Disable-Mailbox or Remove-Mailbox command completes. Exchange retains disabled mailboxes in the mailbox database based on the deleted mailbox retention settings configured for that mailbox database. After the specified period of time, the mailbox is permanently deleted.

Get-MailboxStatistics -Database "*database*" | where {$_.DisconnectReason -eq "disabled"}
Get-MailboxStatistics -Database "*database*" | where {$_.DisconnectReason -eq "softdeleted"}

Disable-Mailbox -Identity Eugene

$database=get-mailboxdatabase
Remove-StoreMailbox -Identity Eugene -Database $Database -mailboxState Disabled

The user account Eugene is not deleted.

disconnects the user John Rodman's (john) mailbox from the user account and removes the mailbox object from Active Directory. The mailbox remains in the Exchange database for the deleted mailbox retention period configured for the mailbox database.

Remove-Mailbox -Identity Adatum\john

To permanently remove the mailbox without waiting for the retention period.

Remove-StoreMailbox -Identity "Simon Chong" -Database "*database*" -MailboxState disabled
Remove-StoreMailbox -Identity "Merl Emily" -Database "*database*" -MailboxState softdeleted

disconnects the user John Rodman's (john) mailbox from the user account, removes the mailbox object from Active Directory, and removes the mailbox from the Exchange database.

Remove-Mailbox -Identity Adatum\john -Permanent $true