I'm the Exchange Admin for our corp. (The require PIN was enabled on the Exchange Server but even when adding a user to the exception list or disabling the policy on the server, phones were still requiring a PIN.)
If the PIN is not a requirement from your IT department (MS Exchange Server setting), then check the following on your phone. Settings - Location & security - Device administration - Select device administrators. If it is activated, deactivate the one associated with email. Then go to, Settings - Location & security - Change screen lock and select None (or Pattern or whatever you want).
Hope this helps. I spent many days trying to figure out why the phone was holding on to the requirement (and the user even went to the cell store and their techs couldn't find the solution).