If we delete a user account then it will automatically disconnects mailbox from the account and adds to Disconnected Mailbox list. Mailbox will be listed until retention period of 30 days
Get-MailboxStatistics -server <servername> | where { $_.DisconnectDate -ne $null } | select DisplayName,MailboxGuid,Database,DisconnectDate
Gets the list of Disconnected mailbox in the specified Exchange 2007 Server
Get-MailboxStatistics | where { $_.DisconnectDate -ne $null } | select DisplayName,MailboxGuid,Database,DisconnectDate
Gets the list of Disconnected mailbox on the Exchange 2007 maibox server where you are running this command