Email verification issue

Question

Hello, I am developing an app where i want to put email verification. At the time of sign up user will enter email address and if that email address is valid then one link will be sent to users email address and only after clicking on that link user will be able to login to the app. Now my question is after sign up we need to block the user untill he/she clicks on that link. So how to do this usecase on this server. So how to block and Unblock the user in this usecase.