Deactivating Mailboxes
When a mailbox is deactivated, it continues to receive mail, but the user can’t log in. If the user is an admin, they will also be unable to log in to My Account. An admin can reactivate a deactivated mailbox any time, within Mailbox Manager.
Use for Deactivating
Deactivation is generally used by an admin to lock a user out of their mailbox. If you have only one mailbox, you are the admin. You can’t deactivate the user that you’re currently logged in as.