Check this thread they discuss different ways of doing this.
But basically one way is to have a yes/no field on the User say email confirmed? which is set to no by default.
Then create a new confirmation page in your app that the user will be taken to when they click the confirm email link that your application will send.
Then in the sign-up action you check the box "Send an email to confirm the email ", then select the page confirm email page you created above.
On the confirm page add for on page load event add an action to modify the current user’s email confirmed? to yes.
So anytime the user logs in you can check if their email confirmed? is yes or no and take an appropriate action. See this thread for an more details