private function clear() {
        if (!isset($this->phpMailer)) {
            return;
        }
        $this->phpMailer->clearAddresses();
        $this->phpMailer->clearCCs();
        $this->phpMailer->clearBCCs();
        $this->phpMailer->clearReplyTos();
        $this->phpMailer->clearAllRecipients();
        $this->phpMailer->clearAttachments();
        $this->phpMailer->clearCustomHeaders();
    }