To undo accidental deletion of emails:

1. Check the Deleted Items folder or Trash to see if the email is there.
2. Retrieve the item if it is already in the folder.
3. If the email is not in the Deleted Items folder, check if you can find it in the Recoverable Items folder.
4. If the email is not in the Recoverable Items folder either, then open the Recoverable Items folder and enter a date range to search for the email.
5. Select the emails that you want to recover and click the Restore button.