Here are the steps to take if you need to recover an email that was accidentally sent to trash:

1. Open the trash folder.
2. If the email is in the trash folder, click and drag the email to the inbox folder.
3. If the email is not visible in the trash folder, go to the Deleted Items Retention window.
4. Select the Restore option. This should move the message from the trash folder to the inbox folder.
5. If the message is no longer in the deleted Items Retention window, the message will be removed from the system and cannot be recovered.