On our iPads that use anything below iOS7, email works fine. Anything using iOS7 and above, the iPads will not sync email on our internal network. If I am using WiFi outside of the business, it works fine. For example, at home, on WiFi, the iPad sync's the Exchange email fine. Inside the office, it will not.
We have removed/added email accounts but did not work. I did read something about activesync not working correctly with iOS7, but said that it was an issue with iOS7.