Validate bulk mail list using NPM package `email-deep-validator`.

mail-validate.js

const EmailValidator = require('email-deep-validator');
const path = require('path');
const fs = require('fs');
const throat = require('throat');

const emailValidator = new EmailValidator();

const wait = ms => new Promise(resolve => setTimeout(resolve, ms));

const retry = async (fn, retryCount = 2, intervalMs = 500, originalError = null) => {
  if (retryCount === 0) {
    if (!originalError) throw new Error('Failed after 3 retries');
    throw originalError;
  }
  try {
    const res = fn();
    if (res && typeof res.catch === 'function') {
      return res.catch(err => wait(intervalMs).then(() => retry(fn, retryCount - 1, intervalMs, err)));
    }
    return res;
  } catch (err) {
    await wait(intervalMs);
    return retry(fn, retryCount - 1, intervalMs, err);
  }
};

const validate = async address => {
  try {
    const { wellFormed, validDomain, validMailbox } = await retry(() => emailValidator.verify(address));
    return wellFormed !== false && validDomain !== false && validMailbox !== false;
  } catch (err) {
    return true;
  }
}

const main = async (fileIn, fileOut) => {
  if (!fileIn) {
    console.error('Filename is empty, e.g. `node mail-validate.js emails.txt`')
    process.exit(1);
    return;
  }
  console.log(`Validation started...`);
  const items = fs.readFileSync(path.join(__dirname, fileIn)).toString().split('\n').map(e => e.trim());
  const emailRegex = /.*<(.*?)>/;
  const filteredItems = (await Promise.all(items.map(throat(50, async item => {
    const email = item.includes('<') ? item.match(emailRegex)[1] : item;
    const isCorrect = await validate(email);
    console.log(`${email}: ${isCorrect ? '✅' : '⛔️'}`);
    return isCorrect ? item : null;
  })))).filter(e => !!e);
  console.log(`Done: ${filteredItems.length} out of ${items.length} are valid`);
  fs.writeFileSync(path.join(__dirname, fileOut), filteredItems.join('\n'));
  process.exit(0);
}

main(process.argv[2], process.argv[3] || 'out.txt');