For mailbox protection, mailboxes are associated with one default User Mailbox subclient.
You can associate individual mailboxes, mailboxes within a database, and mailboxes within an Active Directory group (AD group). You can add mailboxes to the subclient using any of those groupings.
Autodiscovery
If you add mailboxes by databases or by AD groups, it might take a long time to discover the mailboxes right away if your organization is very large. You have the option to autodiscover the mailboxes in the groups later when the domain is scanned and the mailboxes are discovered at that time. Typically, this occurs once every 24 hours. If you choose to autodiscover mailboxes later, the mailboxes do not appear in the Mailboxes list until after they have been discovered.
Note
Autodiscovery is not supported for dynamic AD groups.
User Mailbox Status
Active: Active Mailboxes do consume a license.
Disabled: Once the User Mailbox is disabled, you cannot run any archiving or cleanup jobs. You can run browse, restore and content indexing operations on disabled user mailboxes.Disabled Mailboxes do not consume a license.
Deleted: You can run browse, restore and content indexing operations on deleted user mailboxes. Deleted Mailboxes do not consume a license.
Exchange Policies
You can assign Exchange policies to the mailboxes at the time that you associate them with the subclient or later. We recommend that you assign the archive policy immediately so that your mailboxes are protected.