Send email with Express.js

Prerequisites

Node.js 16 or later
An Express 4 or Express 5 project
Authorize your sending domain
Create or retrieve your SendLayer API key

Installation

Install the SDK alongside Express and dotenv.

npm install express sendlayer dotenv

yarn add express sendlayer dotenv

pnpm add express sendlayer dotenv

Storing your API key

Create a .env file in your project root and add the key.

.env

SENDLAYER_API_KEY=your-api-key
PORT=3000

Add .env to .gitignore so the key never reaches version control.

Creating the email client

Initialize the client in its own module and export it. A single instance serves every route in the application.

src/sendlayer.js

import 'dotenv/config';
import { SendLayer } from 'sendlayer';

if (!process.env.SENDLAYER_API_KEY) {
  throw new Error('SENDLAYER_API_KEY is not set');
}

export const sendlayer = new SendLayer(process.env.SENDLAYER_API_KEY);

The startup check fails fast on a missing key. Without it, the first request would be the place the problem surfaces.

These examples use ES modules. Add "type": "module" to your package.json, or convert the imports to require() calls if your project uses CommonJS.

Sending an email from a route

Add a POST route that reads JSON from the request body and calls Emails.send().

src/server.js

import express from 'express';
import { sendlayer } from './sendlayer.js';

const app = express();
app.use(express.json());

app.post('/api/send-email', async (req, res) => {
  const { name, email, message } = req.body;

  const response = await sendlayer.Emails.send({
    from: { email: 'sender@example.com', name: 'Acme Support' },
    to: [{ email: 'support@example.com', name: 'Support Team' }],
    replyTo: [{ email, name }],
    subject: `New message from ${name}`,
    text: message,
  });

  res.status(200).json({ messageId: response });
});

const port = process.env.PORT || 3000;
app.listen(port, () => {
  console.log(`Server listening on port ${port}`);
});

The express.json() middleware parses the request body. Without it, req.body is undefined.

The sender email address must match a domain you have authorized in SendLayer.

Validating input before sending

Reject malformed requests before they reach the API. This saves a round trip and returns a clearer error to the caller.

src/routes/email.js

import express from 'express';
import { sendlayer } from '../sendlayer.js';

const router = express.Router();

router.post('/send-email', async (req, res, next) => {
  const { email, subject, message } = req.body;

  if (!email || !subject || !message) {
    return res.status(400).json({
      error: 'The email, subject, and message fields are required.',
    });
  }

  try {
    const response = await sendlayer.Emails.send({
      from: 'sender@example.com',
      to: email,
      subject,
      text: message,
    });

    res.json({ messageId: response });
  } catch (error) {
    next(error);
  }
});

export default router;

Mount the router in your application file.

src/server.js

import express from 'express';
import emailRoutes from './routes/email.js';

const app = express();
app.use(express.json());
app.use('/api', emailRoutes);

Sending HTML emails

Add the html parameter for rich content. Include text as a fallback for clients that block HTML.

src/routes/welcome.js

import express from 'express';
import { sendlayer } from '../sendlayer.js';

const router = express.Router();

router.post('/welcome', async (req, res, next) => {
  try {
    const response = await sendlayer.Emails.send({
      from: { email: 'hello@example.com', name: 'Acme' },
      to: req.body.email,
      subject: 'Welcome to Acme',
      html: `
        <html>
          <body>
            <h1>Welcome aboard</h1>
            <p>Your account is ready. <a href="https://example.com/login">Sign in</a> to get started.</p>
          </body>
        </html>
      `,
      text: 'Your account is ready. Sign in at https://example.com/login to get started.',
      tags: ['welcome-email'],
    });

    res.json({ messageId: response });
  } catch (error) {
    next(error);
  }
});

export default router;

The tags array labels the message. Tags show up in your event history, which helps you separate welcome emails from other traffic.

Testing the endpoint

Start the developmentserver.

node src/server.js

Then post a request from another terminal using cURL.

curl --request POST \
  --url http://localhost:3000/api/send-email \
  --header 'Content-Type: application/json' \
  --data '{
  "name": "Paulie Paloma",
  "email": "paulie@example.com",
  "message": "Testing the send endpoint."
}'

A successful request returns the message ID:

{
  "messageId": "06e4491f-fc5a-49cb-bc57-xxxxxx"
}

Open the Email logs page in your SendLayer dashboard to confirm delivery.

Next steps

Node.js SDK Reference

Review every method and parameter in the Node.js SDK.

Managing Webhooks

Create, list, and delete webhook subscriptions.

Retrieving Events

Query delivery events for any message.

Rate Limits

Understand recipient and request limits.

Getting Started

SDKs

Guides

Integrations

Releases

Prerequisites

Installation

Storing your API key

Creating the email client

Sending an email from a route

Validating input before sending

Sending HTML emails

Testing the endpoint

Next steps

Node.js SDK Reference

Managing Webhooks

Retrieving Events

Rate Limits

​Prerequisites

​Installation

​Storing your API key

​Creating the email client

​Sending an email from a route

​Validating input before sending

​Sending HTML emails

​Testing the endpoint

​Next steps

Node.js SDK Reference

Managing Webhooks

Retrieving Events

Rate Limits

Prerequisites

Installation

Storing your API key

Creating the email client

Sending an email from a route

Validating input before sending

Sending HTML emails

Testing the endpoint

Next steps