Removing old recently emailed addresses

I've tried everything suggested online but nothing works, how can I delete all the old recently emailed list from my inbox. I know how to go to options and click only show people in my contact list but I want to remove them forever. When I type in an A-Z in the To: or Ccc/Bcc all the people with that letter pops up. If I could just delete the recently emailed list that would go away. Can anyone in tech support explain!!