Some Exchange Administrators overlook setting retention limits on mailboxes. This is very important in businesses without mailbox quotas, because most users will never empty their deleted items. Also, setting the empty deleted items GPO will upset your users.
This step-by-step will show you how to only retain the last X number of days in the deleted items folder.
1.Open Exchange Management Console and Navigate to Organization Configuration -> Mailbox.
2.Select Managed Default Folders Tab and you should see the Deleted Items folder
3.Right Click on Deleted Items folder and Select New Managed Content Settings
4.Name your new policy “X number of days retention policy”
5.Define the retention period in the wizard
6.Click Next and skip the journaling screen
7.Review Summary Screen and click New
Once you policy is made you will need to set it for specific users, you can do this manually but I’d recommend just do it in bulk to your OU that the users are under in Active Directory. (Note: If your users are all under the Users folder and not in a OU you made, I’d recommend making one as it will not only help you here, but in many places in the future as well.)
Simply run the following command and you will set the mailbox policy on all the users in your Organizational Unit (OU)
Get-Mailbox -OrganizationalUnit SBSUsers | Set-Mailbox -ManagedFolderMailboxPolicy “Deleted Items”
Now, your policy is in effect and it should be enforced overnight and when you walk in tomorrow, you’ll notice all deleted items only go back 90 days.