If you've deleted a message accidentally, you can recover it using the following steps:

1. Check the Deleted Items folder. You can recover the item by dragging it to another folder.
2. If you need an email that you sent to the recycle bin, and you’ve already emptied the Deleted Items folder, select the Deleted Items folder.
3. From the Tools menu, select Recover deleted items.
4. Select the item(s) you wish to recover, and click the Recover selected items button on the toolbar.