In the Control Panel, double-click the "Mail" icon. CLick "Email Accounts" button. Choose "View or change existing accounts", and click "Next" button. Click "Change" button. Click "More settings" button. Click "Advanced" tab. Change the "logon network security" from "none" to "Password Authentication".
This change is just a regsitry setting somewhere, so if you used regedit while you are doing the change you should be able to find the variable.