iPad is frozen on email, can't delete, move, or go to mail box

Close the Mail app in the Task Bar and re-launch.

Double-click the Home button to reveal Task Bar. Hold Mail app down for a second or two; tap the minus sign to close app.

If it still doesn't work, try a reset.

Hold the Sleep and Home button down (together) for about 10 seconds until you see the Apple logo. Ignore the red slider.

Try closing the Mail app completely and see if it works properly when you re-open the app : from the home screen (i.e. not with the Mail app 'open' on-screen) double-click the home button to bring up the taskbar, then press and hold any of the apps on the taskbar for a couple of seconds or so until they start shaking, then press the '-' in the top left of the Mail app to close it, and touch any part of the screen above the taskbar so as to stop the shaking and close the taskbar.

If that doesn't work also do a reset : press and hold both the sleep and home buttons for about 10 to 15 seconds (ignore the red slider), after which the Apple logo should appear - you won't lose any content, it's the iPad equivalent of a reboot.