Microsoft Office 365 licensing plans give you a very large amount of mailbox storage (up to 100 GB). Office 365 also has built-in features to retain and archive mailboxes without additional costs. The need to back up Office 365 mailbox content for storage reasons is generally not needed. However, there are other business reasons why an organization may need to archive mailbox and public folder content in Office 365.
For example, what happens when an employee leaves the company and there are policies that require to archive all user data and mails elsewhere for compliance purposes? At the time of deprovisioning a user, administrators follow a set of guidelines to take backups of the user’s mailbox and OneDrive content. Or, what happens when multiple tenants from different businesses are being merged and all unwanted mailboxes need to be removed from Office 365 and archived? Removing unwanted user licenses and thus mailboxes, results in saving license costs. For all such reasons and more, Administrators need to back up and archive Office 365.