private function create() {
        $m = new \PHPMailer();
        switch ($this->protocol) {
            case 'sendmail':
                $m->isSendmail();
                break;
            case 'smtp':
                $m->isSMTP();
                $m->Host = $this->smtpHost;
                $m->SMTPAuth = false;
                $m->SMTPAutoTLS = false;
                $m->Port = $this->smtpPort;
                break;
            case 'mail':
                $m->isMail();
                break;
            case 'qmail':
                $m->isQmail();
                break;
            default:
                throw new \Exception('bad phpmailerType: '.$this->protocol);
        }
        return $m;
    }