Sendgrid ICS附件不起作用

Question

您好我想用电子邮件实现ics附件。我试过下面的代码，但它没有用。

 $ical = "BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//hacksw/handcal//NONSGML v1.0//EN
BEGIN:VEVENT
UID:" . md5(uniqid(mt_rand(), true)) . "#test.com
DTSTAMP:" . gmdate('Ymd').'T'. gmdate('His') . "Z
DTSTART:19970714T170000Z
DTEND:19970715T035959Z
SUMMARY:New event
END:VEVENT
END:VCALENDAR";  
        $email = new SendGrid\Email();

        $email->addTo($email_to)
            ->setFrom($email_from)
            ->setFromName($email_from_name)
            ->setReplyTo($email_reply)
            ->setSubject($email_subject)
            ->setHtml($email_message)
            ->setAttachment($ical);