Both Outlook and Outlook Web App (OWA) give you the ability to restore deleted items for 14 days after deletion.
When you delete an item it gets put in the Deleted Items folder in your mailbox. The Deleted Items folder is the first stage of the items being actually deleted.
When an item gets put into your Deleted Items folder, it remains there for 30 days before it is automatically purged. Once purged, you still have the ability to retrieve the message for a further 14 days using OWA’s “Recover Deleted Items” function.
When an item gets put into your Deleted Items folder, it remains there until you manually empty the folder. Once purged, you still have the ability to retrieve the message for a further 14 days using OWA or Outlook’s Recover Deleted Items function.
Navigate to the folder where the item was deleted from (this will typically be your Deleted Items folder, however if you have hard-deleted (shift-delete) then this may be the original location.