protected function _resolveClassName($class)
    {
        if (is_object($class)) {
            return $class;
        }

        $className = App::className($class, 'Mailer/Transport', 'Transport');

        if (!$className) {
            $className = App::className($class, 'Network/Email', 'Transport');
            if ($className) {
                deprecationWarning(
                    'Transports in "Network/Email" are deprecated, use "Mailer/Transport" instead.'
                );
            }
        }

        return $className;
    }