public function queue($ts = null)
    {
        $recipients = $this->to();
        $author     = $this->from();
        $subject    = $this->subject();
        $msgHtml    = $this->msgHtml();
        $msgTxt     = $this->msgTxt();
        $campaign   = $this->campaign();
        $queueId    = $this->queueId();

        foreach ($recipients as $to) {
            $queueItem = $this->queueItemFactory()->create(EmailQueueItem::class);

            $queueItem->setTo($to);
            $queueItem->setFrom($author);
            $queueItem->setSubject($subject);
            $queueItem->setMsgHtml($msgHtml);
            $queueItem->setMsgTxt($msgTxt);
            $queueItem->setCampaign($campaign);
            $queueItem->setProcessingDate($ts);
            $queueItem->setQueueId($queueId);

            $res = $queueItem->save();
        }

        return true;
    }