SMTP Server Setup for Sending Email from Website

Setting Up Email Sending via SMTP Server

SMTP is the basic transport protocol for email. Used when you don't want to pay for an ESP or when an application runs inside corporate infrastructure with its own mail server (Postfix, Exim, Microsoft Exchange).

Sending via Nodemailer

npm install nodemailer
npm install -D @types/nodemailer

import nodemailer from 'nodemailer';

const transporter = nodemailer.createTransport({
  host: process.env.SMTP_HOST,        // smtp.gmail.com, smtp.yandex.ru, etc.
  port: Number(process.env.SMTP_PORT ?? 465),
  secure: true,                        // true for 465, false for 587
  auth: {
    user: process.env.SMTP_USER,
    pass: process.env.SMTP_PASS,
  },
  // For corporate SMTP with self-signed certificates
  tls: {
    rejectUnauthorized: process.env.NODE_ENV === 'production',
  },
});

// Check connection at server startup
await transporter.verify();
console.log('SMTP ready');

Sending Email

async function sendEmail(params: {
  to: string | string[];
  subject: string;
  html: string;
  text?: string;
  attachments?: nodemailer.Attachment[];
}) {
  const info = await transporter.sendMail({
    from: `"Acme Support" <[email protected]>`,
    to: params.to,
    subject: params.subject,
    html: params.html,
    text: params.text,
    attachments: params.attachments,
    headers: {
      'X-Mailer': 'Acme App v2',
    },
  });

  return info.messageId;
}

// Example with PDF attachment
await sendEmail({
  to: '[email protected]',
  subject: 'Your Invoice #INV-2026-042',
  html: invoiceHtml,
  attachments: [
    {
      filename: 'invoice-2026-042.pdf',
      content: pdfBuffer,
      contentType: 'application/pdf',
    },
  ],
});

Connection Pool for High Load

When sending many emails, create a pool instead of one transport:

const poolTransporter = nodemailer.createTransport({
  pool: true,
  maxConnections: 5,       // parallel connections
  maxMessages: 100,        // messages per connection before reconnect
  host: process.env.SMTP_HOST,
  port: 465,
  secure: true,
  auth: { user: process.env.SMTP_USER, pass: process.env.SMTP_PASS },
});

Popular SMTP Providers

Timeline

SMTP setup with Nodemailer — 1–2 days.