Send email with Node.js (Nodemailer) over SMTP

npm install nodemailer

import nodemailer from "nodemailer";

const transporter = nodemailer.createTransport({
  host: process.env.SMTP_HOST || "smtp.queensmtp.com",
  port: Number(process.env.SMTP_PORT || 587),
  secure: Number(process.env.SMTP_PORT) === 465,   // true = implicit TLS (465); false = STARTTLS (587/2525)
  auth: { user: process.env.SMTP_USER, pass: process.env.SMTP_PASS },
  pool: true,            // reuse connections for batches
  maxConnections: 3,
  maxMessages: 100,
});

await transporter.verify();   // throws if host/port/auth are wrong — do this at startup

const info = await transporter.sendMail({
  from: '"Your App" <hello@yourdomain.com>',      // verified sending domain
  to: "customer@example.com",
  replyTo: "support@yourdomain.com",
  subject: "Your receipt",
  text: "Thanks for your order #1042",
  html: "<h1>Thanks for your order</h1><p>#1042 is confirmed.</p>",
  // attachments: [{ filename: "invoice-1042.pdf", path: "/tmp/invoice-1042.pdf" }],
});
console.log("queued as", info.messageId, info.response);