Node.js Code Example for mySMTP with Nodemailer

Nodemailer is the most popular email library for Node.js. You can connect to mySMTP with STARTTLS on port 587 and verify the connection before sending.

Prerequisites

Node.js 18 or later
Your mySMTP username and password from the setup email
Your mySMTP hostname from the setup email (shown as relayxx.mysmtp.com in these examples)

Install Nodemailer

npm install nodemailer

yarn add nodemailer

pnpm add nodemailer

Basic send example

const nodemailer = require('nodemailer');

const transporter = nodemailer.createTransport({
  host: process.env.MYSMTP_HOST || 'relayxx.mysmtp.com',
  port: 587,
  secure: false,
  requireTLS: true,
  auth: {
    user: process.env.MYSMTP_USER,
    pass: process.env.MYSMTP_PASS,
  },
});

async function sendEmail() {
  const info = await transporter.sendMail({
    from: '"Your Name" <you@yourdomain.com>',
    to: 'recipient@example.com',
    subject: 'Test email from Node.js',
    text: 'This is a plain text test message sent through mySMTP.',
  });

  console.log('Message sent successfully');
  console.log('Message ID:', info.messageId);
}

sendEmail().catch(console.error);

Replace relayxx.mysmtp.com with your real hostname from the mySMTP setup email. Load credentials from environment variables, never hardcode them in source files.

Verify the connection before sending

const nodemailer = require('nodemailer');

const transporter = nodemailer.createTransport({
  host: process.env.MYSMTP_HOST || 'relayxx.mysmtp.com',
  port: 587,
  secure: false,
  requireTLS: true,
  auth: {
    user: process.env.MYSMTP_USER,
    pass: process.env.MYSMTP_PASS,
  },
});

async function verifyAndSend() {
  try {
    await transporter.verify();
    console.log('Server is ready to take our messages');

    const info = await transporter.sendMail({
      from: '"Your Name" <you@yourdomain.com>',
      to: 'recipient@example.com',
      subject: 'Test email from Node.js',
      text: 'This is a plain text test message sent through mySMTP.',
    });

    console.log('Message sent successfully');
    console.log('Message ID:', info.messageId);
  } catch (err) {
    console.error('Error:', err.message);
  }
}

verifyAndSend();

HTML email with attachment

const nodemailer = require('nodemailer');

const transporter = nodemailer.createTransport({
  host: process.env.MYSMTP_HOST || 'relayxx.mysmtp.com',
  port: 587,
  secure: false,
  requireTLS: true,
  auth: {
    user: process.env.MYSMTP_USER,
    pass: process.env.MYSMTP_PASS,
  },
});

async function sendHtmlEmail() {
  const info = await transporter.sendMail({
    from: '"Your Name" <you@yourdomain.com>',
    to: 'recipient@example.com',
    subject: 'HTML email with attachment',
    text: 'This is the plain text fallback.',
    html: '<h1>Hello</h1><p>This is an HTML message.</p>',
    attachments: [
      {
        filename: 'invoice.pdf',
        path: '/path/to/invoice.pdf',
      },
    ],
  });

  console.log('Message sent successfully');
  console.log('Message ID:', info.messageId);
}

sendHtmlEmail().catch(console.error);

Always set requireTLS: true when using port 587. This prevents Nodemailer from falling back to an unencrypted connection if TLS negotiation fails.

Common errors

535 Authentication failed

Your username or password is incorrect, or your account is not yet activated. Re-enter credentials exactly as shown in the setup email. See Setting up SMTP credentials.

Connection timeout or refused

Your network or host may block port 587. Try port 2525 with the same settings, or port 465 with secure: true. See Supported SMTP ports and encryption.

TLS handshake failure

The secure and requireTLS settings do not match the port. For port 587, use secure: false and requireTLS: true. For port 465, use secure: true and remove requireTLS.

Test your SPF, DKIM, and DMARC setup with the mySMTP Deliverability Toolbox before sending large volumes.

Home

API & Webhooks

Node.js Code Example for mySMTP with Nodemailer

Prerequisites

Install Nodemailer

Basic send example

Verify the connection before sending

HTML email with attachment

Common errors

​Prerequisites

​Install Nodemailer

​Basic send example

​Verify the connection before sending

​HTML email with attachment

​Common errors

​Related articles

Prerequisites

Install Nodemailer

Basic send example

Verify the connection before sending

HTML email with attachment

Common errors

Related articles