protected function _attachments(Email $email, array $message = [])
    {
        foreach ($email->getAttachments() as $filename => $attach) {
            $content = isset($attach['data']) ? base64_decode($attach['data']) : file_get_contents($attach['file']);
            $message['files'][$filename] = $content;
            if (isset($attach['contentId'])) {
                $message['content'][$filename] = $attach['contentId'];
            }
        }

        return $message;
    }