Node.js 将express与NodeEmailer一起使用

我正在尝试使用SendGrid和NodeEmailer设置一个express应用程序来发送电子邮件。我已经让我的香草节点应用程序发送电子邮件，但我还没有完全弄清楚如何路由应用程序。有关于如何发送应用程序的想法吗？这就是我到目前为止所做的：

var express = require('express');
var router = express.Router();
var app = express();

app.post('/postEmail', function (req, res) {

var nodemailer = require('nodemailer');
var sendgridTransport = require('nodemailer-sendgrid-transport');


//insert api keys
var credentials = {
    auth: {
        api_key:'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
    }
};

 //create new mailer using the SendGrid transport
var createMail = nodemailer.createTransport(sendgridTransport(credentials));

var emailBody = {
    to: ['xxx@xx.com'],
    from: 'xxx@xx.com',
    subject: 'xx',
    text: 'xxx'
};

 //send the email
createMail.sendMail(emailBody, function (err, res) {
    if (err) {
        console.log(error)
    }
    console.log(res);
 });


});

// finalize the routers to be used and register them
app.use('/', router);

//start the server on the specified port
app.listen(2021);
console.log('You can access the API on port ' + 2021+".");