Well I guess I dont understand what you have in mind with
($_GET['page']
when your form is a POST, not a get, and 'page' is not a var on that form anyway, so that is strike 2, and with PHP its ONE strike you are out. So, is what you are asking for is a validation routine for an email address? Cause that sure doesnt sound like where you were going at first. So maybe instead of not enough info we have too much?