CI_Form_validation::valid_email PHP Method

    public function valid_email($str)
    {
        if (function_exists('idn_to_ascii') && ($atpos = strpos($str, '@'))) {
            $str = substr($str, 0, ++$atpos) . idn_to_ascii(substr($str, $atpos));
        }
        return (bool) filter_var($str, FILTER_VALIDATE_EMAIL);
    }