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Cover image for Part 2 - Building a Full Stack Contact Form: Node.js Backend 2023
Elena Diaz
Elena Diaz

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Part 2 - Building a Full Stack Contact Form: Node.js Backend 2023

Welcome to Part 2 of our Full Stack Contact Form Series! We're about to unlock the world of backend development to enable the actual sending of emails. Get ready to harness the power of Node.js, Express, Nodemailer, CORS, and HTTPS to create a seamless communication experience. By the end of this guide, you'll have hands-on experience on how these technologies work together to bring your contact form to life.


Backend Development

Our journey into the backend realm begins with Node.js (I'm using version 18.13.0) and the npm package manager. These tools will be your trusty companions as we embark on building the backbone of our email-sending mechanism. So, let's roll up our sleeves and get started on creating a backend that ensures your contact form is not just eye-catching, but fully functional too.

Creating Your Node.js Project with npm

Let's kick off our backend development by setting up a Node.js project using npm. This will provide the foundation for building the functionalities that power your email-sending mechanism.

  1. Create a Dedicated Backend Folder: Begin by creating a folder specifically for your backend code. Open this folder in your preferred code editor, like VSCode.

  2. Initialize the Project: In the terminal within your backend folder, enter the following command to generate a basic package.json template file:

npm create -y
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This will initialize your Node.js project and set up the essential package.json file.

  1. Structure Your Files: Create two important files within your backend folder:
  • server.js: This is where you'll write the core functionality code for your backend.
  • config.js: Utilize this file to store email configuration details.

Here's how your project folder might be structured:

    ├── package.json
    ├── server.js
    ├── config.js

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With these foundational steps complete, you've set the stage for your backend development journey. The package.json file will hold key information about your project, and the server.js file will become the heart of your email-sending mechanism. The config.js file will be where we store our constant variables. In the next section, we'll dive into creating the server and setting up the functionalities that bring your contact form to life.

Installing Essential Dependencies (Express, Nodemailer)

Now, let's equip your backend with the necessary tools to bring your email-sending mechanism to life.

Technologies utilized in this project are:

  • Node.js: A runtime environment enabling the execution of JavaScript code on the server-side.
  • Express: A streamlined and versatile web application framework built for Node.js, optimized for routing and middleware management.
  • Nodemailer: A specialized Node.js module designed to simplify the process of sending emails within applications.
  • CORS: An Express middleware that facilitates Cross-Origin Resource Sharing, allowing seamless handling of HTTP requests across varying origins.

Let's install the required dependencies that make the magic happen.

  1. Installing Dependencies: In your terminal, navigate to your backend folder and install the required dependencies using the following commands:
   npm install express nodemailer cors --save
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This will add express, nodemailer, and cors to your project, enabling you to create a functional server and send emails.

  1. Updating Your package.json: Open your package.json file and add the following mailstart entry to your scripts section:
"scripts": {
            "test": "echo \"Error: no test specified\" && exit 1",
            "mailstart": "node server.js"
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and change the main field from config.js to server.js.

"main": "server.js",
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The full package.json should look like this:

        "name": "contactform_backend",
        "version": "1.0.0",
        "description": "",
        "main": "server.js",
        "scripts": {
            "test": "echo \"Error: no test specified\" && exit 1",
            "mailstart": "node server.js"
        "keywords": [],
        "author": "",
        "license": "ISC",
        "dependencies": {
            "cors": "^2.8.5",
            "express": "^4.18.2",
            "nodemailer": "^6.9.4"
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This updated package.json includes scripts to start your server and lists the dependencies your backend relies on. With these dependencies installed and your package.json updated, your backend is armed with the tools it needs to function effectively.

Storing Data Constants in config.js

The config.js file is where you'll store the email configuration details, such as credentials for sending emails and predefined messages.

  1. Populate with Credentials: In config.js, insert the following code:
// change the following details with your information
    module.exports = {
        USER: '',
        PASS: 'password',
        EMAIL: '',
        HOST: '',
        MAILPORT: 555,
        YOURNAME: 'Your Name',
        YOURSITE: '',
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Replace the placeholders with the actual credentials and information that correspond to the domain email account created on (see part 1). These details are essential for successfully sending emails using Nodemailer.

  • USER: Username of email account (domain email address set up in part 1)
  • PASS: Password of email account
  • EMAIL: Email address
  • HOST: SMTP host
  • MAILPORT: STMP port, usually 587
  • YOURNAME: Your full name for the sender and auto reply message
  • YOURSITE: Your portfolio website

Example of domain email credentials:

whois email information

Setting Up Your server.js Backend File

Your server.js file is the heart of your backend. Here you'll configure routes, send emails, and make sure everything runs smoothly. Let's dive in and set up the initial structure.

  1. Importing Required Packages and Initial Setup: Start by importing the necessary packages and setting up the initial configuration:
var express = require('express');
var router = express.Router();
var nodemailer = require('nodemailer');
var cors = require('cors');
const fs = require('fs');
const creds = require('./config');

const app = express();
app.use('/', router);
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  1. Creating a Test Route: Let's create a basic test route to ensure your backend is up and running:
app.get('/', (req, res) => {
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  1. Listening to the Port: Finally, set your backend to listen on a specific port (in this case, port 5000):
app.listen(serverPort, () => console.log(`backend is running on port ${serverPort}`));
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  1. Testing the Backend: To test your backend, run the following command in your terminal:
npm run mailstart
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A successful start of your backend will be indicated in the terminal. You can also open your browser and navigate to http://localhost:5000 to see the "hi" message.

localhost message

With your server.js file set up and now listening on port 5000, your backend is ready to go to respond to requests!

terminal output

As we make updates to the backend, it's important to note that we'll need to stop and start it for the changes to take effect.

To turn off the backend, press Ctrl + C in the terminal where the backend is currently running.

To turn on the backend, run this command again:

npm run mailstart
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Creating Nodemailer Functions for Email Sending

Let's bring the power of Nodemailer into your backend to enable the actual sending of emails. We'll start by configuring Nodemailer using the details from your Whois email information.

  1. Setting Up Transport Configuration: Create the transport object, which holds the configuration for sending emails. Replace the fields with the details from your Whois email information. This includes the SMTP host, port, user, password, and the email address from which the emails will be sent:
var transport = {
    host: creds.HOST,
    port: creds.MAILPORT,
    auth: {
        user: creds.USER,
        pass: creds.PASS,
    from: creds.EMAIL,
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  1. Creating the Nodemailer Transporter: Next, utilize the transport configuration to create a Nodemailer transporter. This transporter is responsible for sending emails. We'll also use the verify method to ensure that the server is ready to accept messages:
var transporter = nodemailer.createTransport(transport);
transporter.verify((error, success) => {
    if (error) {
    } else {
        console.log('Server is ready to take messages');
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Let's start the backend server. In case of any issues, the terminal will show an error message, usually due to incorrect SMTP settings.

terminal output

Crafting API Routes for Email Handling

Now, we're about to tie everything together by creating API routes that handle email sending requests. These routes will enable your backend to receive data from your frontend, send the message to your email, and even respond with an automated acknowledgment. Exciting, isn't it?'/send', (req, res, next) => {
    var name =;
    var email =;
    var message = req.body.message;
    var senderEmail = `${name} <${creds.EMAIL}>`;
    var yourEmail = `${creds.YOURNAME} <${creds.EMAIL}>`;
    var content = `name: ${name} \n email: ${email} \n message: ${message} `;
    var mail = {
        from: senderEmail,
        to: creds.EMAIL,
        subject: `New Portfolio Message from ${name}`,
        text: content,

//Deliver message from your portfolio to your email address
    transporter.sendMail(mail, (err, data) => {
        if (err) {
                status: 'fail',
        } else {
                status: 'success',

            //If Success, send Auto Reply email
                    from: yourEmail,
                    to: email,
                    subject: 'Message received',
                    text: `Hi ${name},\nThank you for sending me a message. I will get back to you soon.\n\nBest Regards,\n${creds.YOURNAME}\n${creds.YOURSITE}\n\n\nMessage Details\nName: ${name}\n Email: ${email}\n Message: ${message}`,
                    html: `<p>Hi ${name},<br>Thank you for sending me a message. I will get back to you soon.<br><br>Best Regards,<br>${creds.YOURNAME}<br>${creds.YOURSITE}<br><br><br>Message Details<br>Name: ${name}<br> Email: ${email}<br> Message: ${message}</p>`,
                function (error, info) {
                    if (error) {
                    } else {
                        console.log('Message sent: ' + info.response);
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In this code, the /send route is created to handle POST requests from your frontend. It extracts the name, email, and message from the request body and constructs an email to send to your specified email address. It also sends an auto-reply to the sender using the provided data.

With this code, your backend is now fully equipped to handle email sending requests. The message data will be extracted from the request and sent to your designated email address, while an automatic acknowledgment will be sent back to the sender. Your backend is primed and ready to test.

Testing Your Full-Stack Contact Form Locally

Great job! You're now at the exciting stage of testing your full-stack contact form locally. Follow these steps to see your creation in action:

  1. Start the Backend: Open a terminal window, navigate to the backend folder and run:
npm run mailstart
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This command will fire up your backend server.

  1. Start the Frontend: Open another terminal window, navigate to the frontend folder, and run:
npm run start
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This will start your frontend development server.

  1. Test the Form: With both the backend and frontend servers up and running, open your browser and navigate to the localhost for the frontend. Mine defaults to http://localhost:3000 (use the appropriate port for your frontend server).

Fill out the contact form with some test data with a valid return email and hit the submit button.
sending message

You should see a successful message on the frontend, indicating that the message was sent.
message sent

Try testing the form for issues:

These are covered on the client-side.

  • missing data
  • using an invalid email format

You should see the following error message on the frontend when the form is unable to send the message with:

  • incorrect credentials
  • backend server is turned off


  1. Check Emails: Now, check your email inbox. You should receive an email from the tester's name containing the message details. The sender will also receive an auto-reply acknowledging the message.

Your contact form's mailbox will show the following:
contact message

The sender will receive this auto-reply message:
sender's auto reply

With these steps, you've successfully tested your full-stack contact form locally! 🎇 The messages are being sent from your frontend, processed by your backend, and received in your email inbox. It's a satisfying moment when everything comes together seamlessly.

GitHub Repository for Backend Code

You can find the complete backend code on GitHub.

In the upcoming and final part of this series, we'll delve into the exciting realm of deploying your full-stack contact form, making it accessible online. This step is pivotal as it enables you to amplify your communication capabilities with visitors to your website. Stay tuned for a wealth of valuable insights and practical guidance that will take your project to its grand finale.

As a quick recap, if you haven't already, make sure to catch Part 1: Getting Started & React Frontend Development of this series where we ventured into creating the frontend contact form, skillfully integrating the POST request that seamlessly connects to the backend. Your journey is nearly complete, and the culmination promises to be both enlightening and rewarding. Part 3: Deployment will be the final touches and getting everything ready for deployment.

Happy coding! 🚀🌠

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