I am using OAuth to access Gmail with dotNetOAuth. How can I force Google to return user\'s email address as part of callback after authorization?
By default, Google
In php, apiOauth2Service.php class provides methods to access logged in user info. For this you can use userinfo->get() method. Make sure you also use scope https://www.googleapis.com/auth/userinfo.email.
This will work with same access token. Also you should try looking in other APIs for similar kind of information in return. This is much easier to look through oAuth_playground >> http://code.google.com/apis/explorer/