Sending email using nodemailer not working - node.js

Question

I have this sendMail cloud function here through i am trying to send a simple email. I am not sure what is the mistake i am doing but i keep getting 400 Bad request error on postman whenever i hit this function.
P.S i am adding correct credentials of my gmail account too
Here is my cloud function
const functions = require('firebase-functions');
const cors = require('cors')({origin: true});
const admin = require("firebase-admin");
const bodyParser = require("body-parser");
const nodemailer = require("nodemailer");
var smtpTransport = require('nodemailer-smtp-transport');
let transporter = nodemailer.createTransport(smtpTransport({
service: 'Gmail',
auth: {
user: 'abc#gmail.com',
pass: '12345'
}
}));
//Send email
exports.sendMail = functions.https.onRequest((request, responde) => {
// cors(req, res, () => {
// getting dest email by query string
res.set('Access-Control-Allow-Origin', '*');
res.set('Access-Control-Allow-Methods', 'GET', 'POST');
res.set('Access-Control-Allow-Headers', 'Content-Type');
if(req.method === 'OPTIONS') {
res.end();
}
else
{
if(req.body.dest != null || req.body.dest != undefined) {
const dest = req.query.dest;
const mailOptions = {
from: 'Ehsan Nisar <ABC#gmail.com>',
to: dest,
subject: 'I\'M A PICKLE!!!', // email subject
html: `<p style="font-size: 16px;">Pickle Riiiiiiiiiiiiiiiick!!</p>
<br />
<img src="https://images.prod.meredith.com/product/fc8754735c8a9b4aebb786278e7265a5/1538025388228/l/rick-and-morty-pickle-rick-sticker" />
` // email content in HTML
};
// returning result
return transporter.sendMail(mailOptions, (erro, info) => {
if(erro){
return res.send(erro);
}
return res.send('Sended');
});
}
else {
res.send(400, {
"message": "All fields are required"
})
}
// });
}
});