At the next scheduled maintenance, Exchange and AD U&C will mark the mailbox as detached, and after the deleted items retention period expires, it will be removed.

Hello, When you delete a mailbox from Exchange, all Exchange attributes are removed from the user account in Active Directory. The disconnected mailbox is hidden and scheduled to be deleted.

Delete the mailbox. The disabled mailbox will be kept in the database for a maximum of 14 days. Get-MailboxDatabase Remove-Mailbox -DeleteDATABASE?

Select a mailbox you want to reconnect. and then click Connect a mailbox. Select the disabled mailbox that you want to reconnect, and then connect it by clicking Connect. Accept the warning message by selecting Yes in the window that asks whether you are sure that you wish to reconnect the mailbox.

Select the database in the list view after removing it from Exchange Server. In the toolbar, click the delete button. If you’re sure you want to remove the mailbox database from Exchange Server, a caution message will appear. Select Yes.