$email isn't declared as anything, so that provides no surprise that it produces no output.
Enable your error reporting:
PHP Code:
ini_set('display_errors', 1);
error_reporting(E_ALL);
You can check the $_POST using
var_dump($_POST); to see what's in it. If its empty, it's not receiving post, which indicates that it is receiving a $_GET instead. Did you modify the form action there as well, or was that always post?
Also, this hasn't a thing to do with Mysql. Moving to PHP forum.