title: Nodemailer using gmail, Cannot create property 'mailer' on string 'SMTP'
body: <p>I am trying to send the data from the form I created to my gmail account, when clicking the sumbit button I always get the same error.
  I found a lot of issues about nodemailer, but none of them seem to be the same issue as I am experiencing. </p>
  
  <p>Ofcourse I have stated my clientId but just deleted for this post.</p>
  
  <pre><code>TypeError: Cannot create property 'mailer' on string 'SMTP'
  at Mail (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\nodemailer\lib\mailer\index.js:45:33)
     at Object.module.exports.createTransport (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\nodemailer\lib\nodemailer.js:46:14)
     at C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\src\app.js:39:26
     at Layer.handle [as handle_request] (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\layer.js:95:5)
     at next (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\route.js:131:13)
     at Route.dispatch (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\route.js:112:3)
     at Layer.handle [as handle_request] (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\layer.js:95:5)
     at C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:277:22
     at Function.process_params (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:330:12)
     at next (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:271:10)
     at serveStatic (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\node_modules\serve-static\index.js:75:16)
     at Layer.handle [as handle_request] (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\layer.js:95:5)
     at trim_prefix (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:312:13)
     at C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:280:7
     at Function.process_params (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:330:12)
     at next (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:271:10)
  </code></pre>
  
  <p>this is my app.js: </p>
  
  <pre><code>// require modules
  const express = require('express');
  const app = express();
  const pug = require('pug');
  const fs = require('fs')
  const bodyParser = require('body-parser');
  const pg = require('pg');
  const nodemailer = require('nodemailer');
  const xoauth2 = require('xoauth2');
  
  
  //set view engine and views
  app.set('views', 'src/views');
  app.set('view engine', 'pug');
  
  app.use(bodyParser.urlencoded({extended: false}));
  app.use(express.static('./resources/'));
  
  
  
  
  
  //display index page
  app.get('/', function ( req, res ){
    console.log('Index is displayed on localhost');
      res.render('index');
  });
  
  app.post('/zorginstelling/ziekenhuis-olvg-locatie-west-voorheen-sint-lucas-andreas-ziekenhuis-amsterdam-109428/waardeer', function (req, res) {
    var mailOpts, smtpTrans;
    console.log('form word gepost')
    //Setup Nodemailer transport, I chose gmail. 
    smtpTrans = nodemailer.createTransport('SMTP', {
        service: 'Gmail',
        auth: {
          xoauth2: xoauth2.createXOAuth2Generator({
              user: 'kylevantil14@gmail.com',
              clientId: '-' ,
              clientSecret: '-' ,
              refreshToken: '-'
          })
         }
    });
  
     //Mail options
    mailOpts = {
        from: req.body.rating[name] + ' &amp;lt;' + req.body.rating[email][first] + '&amp;gt;', 
        to: 'kylevantil14@gmail.com',
        subject: 'Test',
        text: req.body.rating[comment] + req.body.rating[questions][behandeling] + req.body.rating[name]
    };
  
      smtpTrans.sendMail(mailOpts, function (error, response) {
        //Email not sent
        if (error) {
            console.log('There was a problem')
        }
        //Yay!! Email sent
        else {
            console.log('Email sent!')
        }
    });
  });
  
  
  
  var server = app.listen(4000, function () {
          console.log('Example app listening on port: ' + server.address().port);
      });
  </code></pre>