Hi. If I want to allow users to sign in on my website, they must first sign up, right? So when signing up, I want to ensure that the email address they provide is actually them on the other end. How can I set up a system that when the user enters an email address it will first ensure that it is real (check DNS) then if it is, send it an email asking the person to verify that they are the one who wants to register at my site? I google'd this and got something called "challenge/response" but I don't know if that's exactly what I want. Does anyone know what I'm looking for? How can it be implemented?