Hi derbzz-have you tried to re-enter your email and password? Try to do this by going to iPad settings/mail, contacts, calendars.
See if that works. Also, of you are using the native mail app-try to quit the app. To do this either do a 4 finger swipe upward or double press the home button. The multi-task bar will show on the bottom-all apps will show. Long press the mail app by pressing the red circle in the corner of app. Than re-try. Let us know if that works or not.
Meanwhile...
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