How do you escape from a email box?

Tap on the name of the account in the upper left corner of the window on the left side. Just keep tapping until you get back to the Mailbox list. You can tap the home button to go back to the home screen as well from the mail app.

If you want to exit the Mail app then press the home button below the screen which should take you back to your iPad homescreen. If you have an email open and you want to go back to your Inbox so that you can select a different email then tap the Inbox button top left and your emails should be listed - if you hold the iPad in landscape orientation then your emails should be listed down the left-hand side of the app.