On Exchange Online, if you've permanently deleted an item in Microsoft Outlook or Outlook Web App, the item is moved to a folder (Recoverable Items > Deletions) and kept there for 14 days, by default. You can change how long items are kept, up to a maximum of 30 days.

NOTE: you'll need to use PowerShell to change the retention period.

In these examples, we increase the retention period to 30 days, the maximum for Exchange Online mailboxes. But you can set the number to whatever you like, up to that limit.

Example 1

Set Emily Maier's mailbox to keep deleted items for 30 days. In Exchange Management Shell, run the following command:

Set-Mailbox -Identity "Emily Maier" -RetainDeletedItemsFor 30

Example 2

Set all user mailboxes in the organization to keep deleted items for 30 days. In Exchange Management Shell, run the following command:

Get-Mailbox -ResultSize unlimited -Filter {(RecipientTypeDetails -eq 'UserMailbox')} | Set-Mailbox -RetainDeletedItemsFor 30

TipTip: need to keep deleted items for longer than 30 days? To do this, place the mailbox on In-Place Hold or Litigation Hold. This works because when a mailbox is placed on hold, deleted items are kept and retention settings for deleted items are ignored.

Check to be sure the value is changed

NOTE: you'll need to use PowerShell to check the value.

To check for one mailbox, run the following command:

Get-Mailbox <name> | FL RetainDeletedItemsFor

Or to check for all mailboxes, run the following command:

Get-Mailbox -ResultSize unlimited -Filter {(RecipientTypeDetails -eq 'UserMailbox')} | FL Name,RetainDeletedItemsFor

Steps for using PowerShell with Exchange Online (Remainder)

These steps assume you're using Windows 10 or Windows 8 (or 8.1). Open the PowerShell window:

• On your computer, type Windows PowerShell in the taskbar search box.
• When you see the result appear, right-click it, and select Run as administrator. (Why? Because you have to run commands in an "elevated" Windows PowerShell window.)
• When you're prompted to "let this app make changes to your PC," click Yes.
• You'll see a Windows PowerShell window with a prompt like PS C:\WINDOWS\system32.

Make sure PowerShell can run signed scripts; at the prompt in the PowerShell window, run the following command:

Set-ExecutionPolicy RemoteSigned

Connect to Exchange Online with your credentials; at the prompt in the PowerShell window, run the following command:

$UserCredential = Get-Credential

In the Windows PowerShell Credential Request dialog box, type your Office 365 user name and password, and then click OK.
At the prompt in the PowerShell window, run the following command. You can use the "Copy" option to copy it from this page, then just paste it into the PowerShell window.

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection

NOTE: If you are an Office 365 operated by 21Vianet customer in China, use the following value for the ConnectionUri parameter: https://partner.outlook.cn/PowerShell.

Finally, run this command:

Import-PSSession $Session

Now you're ready to run the command to change the retention time for permanently deleted Outlook items.

Be aware

• Estimated time to complete: Assuming you've got PowerShell set up and connected to Exchange Online, this update is really quick—about 2 minutes. If you need to get PowerShell set up, add extra time for that.
• If you want to place a mailbox on In-Place Hold and Litigation Hold so the retention limit is ignored, make sure the mailbox has an Exchange Online (Plan 2) user license.

More about deleted items and retention time

When a user permanently deletes a mailbox item (such as an email message, a contact, a calendar appointment, or a task) in Microsoft Outlook and Outlook Web App, the item is moved to the Recoverable Items folder, and into a subfolder named Deletions.

A mailbox item is deleted and moved to the Recoverable Items folder when a user does one of the following:

• Deletes an item from the Deleted Items folder.
• Empties the Deleted Items folder.
• Permanently deletes an item by selecting it and pressing Shift+Delete.

How long deleted items are kept in the Deletions folder depends on the deleted item retention period that is set for the mailbox. An Exchange Online mailbox keeps deleted items for 14 days, by default. Use the Exchange Management Shell, as shown above, to change this setting, to increase the period up to a maximum of 30 days.

Users can recover, or purge, deleted items before the retention time for a deleted item expires. To do so, they use the Recover Deleted Items feature in Outlook or Office Outlook Web App.