You can recover permanently deleted emails from Apple Mail. You have to go back to the time that the email was deleted. To do this, click on the Time Machine icon. Click back in time using the timeline on the right edge of the screen until you find a backup containing the deleted emails. Then click Restore to recover your emails.
How do I recover permanently deleted emails from Apple Mail?
To recover permanently deleted emails from Apple Mail, you need to delete the account from your device and then delete the emails with the mailboxes.