Comment by Etheryte

That is fair, but I don't think it changes the outcome. The only way you can verify an email address is correct is to send a verification email. If you want to help the user ensure their input was what they intended, having two inputs for the same value is a better way to do that than a regex on a single field. As an example, my email is 20 chars long, the whole email regex thing only validates one or two of those 20 chars and doesn't help against typos in any way. In short, it's a lot of complexity without any real upside.