如何回复线程，以便出现“...”按钮？

Question

我做的就是要求在一个帖子中包含一个回复，即in-reply-to和references标题，相同subject，但收到消息没有想要的“......”按钮。

var message = "below should be a ... button to exapnd the thread history";

emps.push(from); // emps is array of employees. add the original sender as a receiver

var base64EncodedEmail = btoa( // encode email "envelope"
            "Content-Type:  text/html; charset=\"UTF-8\"\n" +
            "Content-length: 5000\n" +
            "Content-Transfer-Encoding: message/rfc2822\n" +
            "to: " + emps.join() + "\n" +
            "from: \"" + config.get('my.name') + "\" <"+ config.get('my.email') +">\n" +
            "In-Reply-To: "+ rfcMsgID + "\n" +
            "References: "+ rfcMsgID + "\n" +
            "subject:" + subject + "\n\n" + // subject is the original message subject
            message
                ).replace(/\+/g, '-').replace(/\//g, '_');
var params = { userId: 'me', auth: oauth2Client, resource: { 
    raw: base64EncodedEmail,
    threadId: message.threadId
}};
gmail.users.messages.send(params, function(err,message){
    if(err){
        console.log('err from google: %s',err)
    }else{
        console.log('success from google: %s',util.inspect(message))
    }
    callback(err,message)
});

我怎样才能让它发挥作用？

（在图片中，我要显示的按钮）