Node.js Sending Emails with Nodemailer

What is Sending Emails with Nodemailer in Node.js?

Nodemailer sends email from Node over SMTP or a transactional provider. It handles HTML bodies, attachments, connection pooling and authentication including OAuth2.

Sending Emails with Nodemailer example

import nodemailer from 'nodemailer';

const transporter = nodemailer.createTransport({
  host: process.env.SMTP_HOST,
  port: 587,
  secure: false,
  auth: { user: process.env.SMTP_USER, pass: process.env.SMTP_PASS },
  pool: true,
  maxConnections: 3,
});

export async function sendWelcome(to, name) {
  await transporter.sendMail({
    from: '"MyInternships" <no-reply@example.com>',
    to,
    subject: 'Welcome aboard',
    text: `Hi ${name}, welcome!`,          // plain-text fallback matters for deliverability
    html: `<p>Hi <b>${name}</b>, welcome!</p>`,
  });
}

Key points to remember

• Create the transporter once at module level, not per email.
• Deliverability depends on SPF, DKIM and DMARC DNS records more than on code.
• Send email in the background — never make a user wait for SMTP.
• Always include a plain-text alternative alongside the HTML.

Common mistakes with Sending Emails with Nodemailer

• Awaiting the send inside a signup request, adding seconds to the response.
• Missing SPF and DKIM records, so mail lands in spam regardless of the code.
• Sending in a tight loop with high concurrency, which many SMTP servers throttle or drop.