In exchange 2007 if you delete any mailbox or any AD user, the mailbox will be there for 30 days in disconnected mailbox view and you can reconnect it again within 30 days if you want to restore the mailbox to its original state. After 30 days the mailbox will be permanently deleted and you can then only restore it from the backup.
Recently i faced a strange issue, one of the mailbox user was deleted by mistake and i am unable to see this user in disconnected mailbox view. The mailbox was deleted 2 days back which is under 30 days threshold but still the mailbox was not visible. After done some research and some help from one of my friend i figured out that i have to run following command in order to make this mailbox visible in disconnected mailbox view
Clean-mailboxdatabase –identity Databasename
As per Microsoft,
“use the Clean-MailboxDatabase cmdlet to scan the Active Directory directory service for disconnected mailboxes that are not yet marked as disconnected in the Microsoft Exchange store and update the status of those mailboxes in the Exchange store. This cmdlet is not able to update the Exchange store unless the Microsoft Exchange Information Store service is running and the database is mounted.
A connected mailbox has two parts: the mailbox object in the Exchange store, and the user object with Exchange properties in Active Directory. A disconnected mailbox is the mailbox object in the Exchange store, but it is not connected to a user object in Active Directory
Under normal circumstances, it is not necessary to run Clean-MailboxDatabase because a mailbox is marked as disconnected immediately after the Disable-Mailbox or Remove-Mailbox command completes. If you used the Disable-Mailbox cmdlet or the Remove-Mailbox cmdlet while the Exchange Information Store service was stopped, or if a mailbox was disabled by an external means other than the Disable-Mailbox cmdlet or Remove-Mailbox cmdlet, you may want to use the Clean-MailboxDatabase cmdlet to scan for disconnected mailboxes.”