Deleted emails and cleared deleted before I knew I had deleted all of them. Can I get my old emails back?

Deleted emails that I want back

Once you have emptied the Trash folder, they are gone. You can check with your email provider and see if they keep backups, but my guess is they are gone.

When you delete an email in your Mail app, it goes to the trash folder. If you empty the Trash folder, the mail is gone.