Uses SMTP communication to validate whether the input email address exists or not

validateEmail.js

const dns = require('dns');
const net = require('net');

const email = process.argv[2];

if (!email) {
  console.error('Please provide an email address as an argument');
  process.exit(1);
}

// Extract the domain from the email address
const domain = email.split('@')[1];

// Look up the MX records for the domain
dns.resolveMx(domain, (err, addresses) => {
  if (err) {
    console.error(`Failed to look up MX records for ${domain}: ${err.message}`);
    process.exit(1);
  }

  if (addresses.length === 0) {
    console.error(`No MX records found for ${domain}`);
    process.exit(1);
  }

  // Connect to the SMTP server
  const socket = net.createConnection(25, addresses[0].exchange);

  socket.on('connect', () => {
    console.log(`Connected to ${addresses[0].exchange}`);

    socket.write(`HELO ${domain}\r\n`, () => {
      console.log('Sent HELO command');

      socket.write(`MAIL FROM:<${email}>\r\n`, () => {
        console.log(`Sent MAIL FROM command for ${email}`);

        socket.end();
      });
    });
  });

  socket.on('error', (err) => {
    console.error(`Error connecting to ${addresses[0].exchange}: ${err.message}`);
    process.exit(1);
  });
});