In iOS 9.1 Mail
  1. Navigate to the mailbox you want to empty
  2. Save the desired messages into another mailbox
    1. Go to one of the messages you want to save
    2. Touch it and move your finger to the RIGHT
    3. Touch Move
    4. select a folder to contain the saved message
    5. repeat the process for each of the messages you want to save
  3. At the top of the window click on Edit and a selection dot will appear next to each of the messages
  4. At the bottom of the window touch Trash All
  5. Confirm Trash All


If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein