title: Google Oauth2 Prevent duplicate email address?
body: <p>I created a website for an organization where users can log in with there <code>gsuite</code> accounts from <code>google</code>, let say, user <code>john</code> logged in using <code>john@doe.com</code>, and do his <code>todos</code>.now imagine  user <code>john</code> left an organization and another new user called <code>john</code>, get the new google account called <code>john@doe.com</code>, when new john gets logged in using google how to check weather its a new gmail or old?</p>