protected function _addRecipient($type, $address, $name = null)
    {
        $classes = $this->_classes;
        $headers = $this->headers();
        if (!isset($headers[$type])) {
            $addresses = $classes['addresses'];
            $headers[$type] = new $addresses();
        }
        $class = $classes['address'];
        $value = new $class($address, $name);
        $headers[$type][] = $value;
        return $value;
    }