I've successfully setup my company email (Microsoft Exchange) in my Lumia 820 and the sync works quite smoothly.
My problem now is when I search for a name via People Hub, I was expecting this will send the query to Exchange via ActiveSync and return answers from the GAL (Global Address List), rather than getting 'Couldn't complete search - we're having trouble searching at the moment. Try again later'.
Message has been the same for the past week on Wi-Fi or mobile data connection. Using my Nokia E72 with the same account, connecting to the GAL works fine. Any suggestions?
Since you have successfully set up the corporate email on the phone, try to go to people hub settings and look for the email account you have set up and try to sync.