public function email($value, $default = false, $checkMxRecord = false)
	{
		if (!$value = filter_var($value, FILTER_VALIDATE_EMAIL)) {
			return $default;
		}
		$dom = explode("@", $value);
		$dom = array_pop($dom);
		if (!$this->url("http://$dom")) {
			return $default;
		}

		return (!$checkMxRecord || checkdnsrr($dom, "MX")) ? $value : $default;
	}