How to detect if an email is a Google Account?

Question

Me and some guys here are working on an start up. We are currently using Google OpenID API to manage registration and login to our app, but we want to migrate to a easier user r

Answer 1

This isn't a complete solution, but you can tell if someone is on Google Apps by looking at their domain's MX records. The link in the answer didn't work for me, so that may be a better solution.