In detail: Exchange Online: Deleted items and mailboxes

Deleted Item Recovery - How do you recover a deleted email?

Exchange Online enables users to restore items they have deleted from any email folder. When an item is deleted, it is kept in a user's Deleted Items folder. It remains there until it is manually removed by the user, or automatically removed by retention policies.

Note

By default, retention policies will automatically remove items from the Deleted Items folder after 30 days, but organizations can customize these retention policies if desired.

After an item has been removed from the Deleted Items folder, the item is kept in a Recoverable Items folder for an additional 14 days before being permanently removed. Users can recover these items using the 

Recover Deleted Items feature in Outlook Web App or Outlook.

If a user has manually purged an item from the Recoverable Items folder, an administrator can recover the item within the same 14 day window, through a feature called Single Item Recovery. This feature allows administrators to conduct a multi-mailbox search to find purged items and then use the search-mailbox PowerShell commandlet to move the items from the discovery mailbox to users’ mailboxes.

Note

The Single Item Recovery period is 14 days by default, but it can be customized in some circumstances.

If an administrator has placed a user’s mailbox on legal hold, purged items are retained indefinitely and the 14-day window does not apply.

Deleted Mailbox Recovery - How do you recover a deleted mailbox?

When an Exchange Online mailbox is deleted, its contents are recoverable for 30 days. A recovered mailbox contains all of the data stored in it at the time it was deleted. After 30 days, the mailbox is not recoverable. Administrators can recover a deleted mailbox using the Exchange Control Panel.

If the mailbox was originally deleted from the Exchange Control Panel and the user's account still exists in the Microsoft Online Services Portal, the administrator can recover the mailbox without assistance. If the user's account was deleted from the Microsoft Online Services Portal, then a call to Office 365 support is required in order to restore the Microsoft Online account so it can be linked to the recovered mailbox.

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