Creating an endpoint that sends emails

Updated: May 2024 Published: Jan 2024 4 min read

The concept here is you have a static site with a contact form, and you want to be able to have your contact form send an email when it is submitted.

One solution is to use nodemailer to send the emails. This post will outline using a serverless function to accomplish this. This function will be a progressive enhancement meaning it will work with or without javascript.

See alternative methods for other options.

Serverless functionLink to the Serverless function section of this page

As far as I am aware it is easiest to handle CORS yourself (instead of API gateway), but I could be wrong about this. If anyone has better ideas please reach out and I’ll update this.

This function is set up for netlify but netlify just uses AWS Lambda functions, just like vercel, so it could be easily hosted on any of the three.

Overview of functionLink to the Overview of function section of this page

  1. Handle CORS / Block origins
  2. Create transporter with nodemailer based on environmental variables
  3. Parse the body of the POST request and optionally validate some fields
  4. Send the email
  5. Return either redirect or json depending on if JS is used to submit the form

Example functionLink to the Example function section of this page

nodemailer-netlify-example, this function takes about 1 second to execute.

Validation with validator.js isEmail and it set up to easily add your own validatio rules based on any fields you have in your form.

It will parse either URLSearchParams or JSON.parse() based on whether there is a "Content-Type": "application/json" header.

This function assumes the form will have the default enctype=application/x-www-form-urlencoded.

Showing success message without JSLink to the Showing success message without JS section of this page

  1. Use a fragment link (/example/#fragment)
  2. Have a dedicated success / error page

I think option 1 is what most users expect, and it’s done with CSS and a returning a redirect to /form/#success when the form is submitted without JS.

<div id="success">Message sent!</div>
#success {
display: none;
#success:target {
display: block;

Structure of formLink to the Structure of form section of this page

Can be anything you want obviously, but the trick to having it work as a progressive enhancement is using the form action and method properties. You’ll also need to be sure to set the headers to properly so the function knows you’re using Javascript to submit.

<form action="" method="POST">
<input type="email" name="email" />
<input type="text" name="subject" />
<textarea name="message" />
<button type="submit">Send</button>
const response = await fetch(form.action, {
method: "POST",
headers: {
"Content-Type": "application/json",
body: JSON.stringify(payload),

Creating email HTMLLink to the Creating email HTML section of this page

Basically it’s tables and inline css, read more on smashing magazine’s complete guide to email html.

React Email is quite nice honestly, it has a dev server and supports Tailwind CSS. I’ve created a work around for an issue with exporting the html directly, react-email-export-workaround.

I’ve taken React Email’s clone of Github Access Token and edited the HTML directly a few times as well. It’s not a bad experience, you can use liveserver to preview it.

Why netlify?Link to the Why netlify? section of this page

Netlify’s free tier allows for commercial use (unlike vercel’s) and the DX compared to AWS Lambda functions made it my go-to platform for serverless functions. I use it to host functions used by sites that aren’t hosted on netlify as well.

AlternativesLink to the Alternatives section of this page

For SMTP I personally use Proton and have heard MxRoute has a good lifetime purchase option for low volume.

If you are using Astro’s hybrid/server output instead of a purely static build, and deploying to either netlify or vercel, you can use nodemailer in an api route inside your project. This will allow you not to worry about CORS and simplify things in general.

If you are deploying to Cloudflare MailChannels is an option, see this blog post for more details.

Another very common solution to this problem, is using a service like Sendgrid, which has a good free tier, or Amazon SES where you pay for what you use. Web3Forms also offers a great free tier. These services will allow you to send email via an API without having to use SMTP directly.

This function could also serve useful if you’re using a service that provides an API and you’d like to do some validation or protect your API key, and if you do this just skip the nodemailer parts and send a fetch request instead.