High Availability and Business Continuity
Microsoft Exchange Online offers extensive retention and recovery support for an organization's email infrastructure. This includes mailbox replication at data centers and the ability to restore deleted mailboxes and deleted items.
Mailbox replication at data centers
Exchange Online mailboxes are continuously replicated to multiple database copies, in geographically dispersed Microsoft data centers, to provide data restoration capability in the event of a local messaging infrastructure failure. For large-scale failures, service continuity management procedures are initiated.
Deleted mailbox recovery
Administrators can delete Exchange Online mailboxes by using the Office 365 admin center to delete the corresponding user account or remove the Exchange Online license, or by using the Remove-Mailbox cmdlet in remote Windows PowerShell. When a mailbox is deleted, Exchange Online retains the mailbox and its contents for 30 days by default. After 30 days, the mailbox is not recoverable. A recovered mailbox contains all of the data stored in it at the time it was deleted. Administrators can recover a deleted mailbox within the retention period by using the Office 365 admin center. To recover a deleted mailbox, administrators have to restore the corresponding Office 365 user account or reassign an Exchange Online license to the user account. For more information, see Delete or Restore User Mailboxes in Exchange Online.
Deleted item recovery
Exchange Online enables users to restore items they have deleted from any email folder, including the Deleted Items folder. When an item is deleted, it's kept in a user's Deleted Items folder. It remains there until it's either manually removed by the user or automatically removed by retention policies. Administrators can customize retention policies in the EAC or by using remote Windows PowerShell.
After an item has been removed from the Deleted Items folder, it's kept in a Recoverable Items folder for an additional 14 days before being permanently removed, but administrators can increase this to a maximum of 30 days by using remote Windows PowerShell. Users can recover the item during this time period by using the Recover Deleted Items feature in Outlook Web App or Outlook. Learn how to change the deleted item retention period.
If a user has manually purged an item from the Recoverable Items folder, an administrator can recover the item within the same time period by using the Single Item Recovery feature with remote Windows PowerShell. By default, Single Item Recovery is enabled when a mailbox is created. To learn more, see Enable or disable single item recovery for a mailbox.
To preserve messages for longer than 30 days in the Recoverable Items folder, organizations can implement longer-term email preservation or time-based In-Place Holds. Learn more about placing a mailbox on In-Place Hold.
To view feature availability across Office 365 plans, standalone options, and on-premise solutions, see Exchange Online Service Description.