Did you buy the iPad second-hand (used)? It sounds if a previous owner has set up 'Activation Lock', though the symptom of this is it asking for an ID (and showing a partial email address) rather than a numerical code.
If a second-hand iOS device has been 'Activation locked' then only the previous owner can unlock it, either by providing you with the account ID and password, or by removing it from his list of devices (as he should have done before selling it) - please see http://support.apple.com/kb/ts4515
If you are unable to contact him to do this then I'm afraid you will not be able to use the device - there is no other way of unlocking it at all. Apple cannot unlock it for you.
You should if possible return it to wherever you bought it and ask for a refund as in this event the device is completely useless.
If on the other hand it's not this but a passcode issue your next step would be to do a full reset and restore from your iTunes backup.