NOTE: Deleted Items are only held for 30 days. After 30 days there is no way to recover them.
Step by step instructions (including screenshots) can be found on the how do I recover Deleted Items? page.
Step by step instructions (including screenshots) see how to recover deleted items through OWA page.
The below can be used within any folder in Outlook, including PST file folders.
It is possible to permanently delete items by using SHIFT + DELETE. Outlook will request confirmation that you want to permanently delete the selected item(s).
NOTE: Once confirmed there is no way to retrieve these items.
Or for additional tips and tricks on deleting emails and folders see the manually deleting unwanted emails/folder page.
Outlook can be set to automatically empty the Deleted Items folder on exiting Outlook by:
NOTE: The above will only work if you close Outlook manually, it will not work if Outlook is forced to close on Shutdown.
Or step by step instructions (including screenshots) can be found on the can Outlook automatically empty Deleted Items? page.
NOTE: Your mailbox size has now been reduced, but will take a little time to reflect this and remove any restrictions.
Or step by step instructions (including screenshots) can be found on the how to manually Empty Deleted Items page.