List Hygiene

function isValidEmailFormat(email) {
  const pattern = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  return pattern.test(email);
}

// Example usage in a signup form
const emailInput = document.getElementById('email');
emailInput.addEventListener('blur', () => {
  if (!isValidEmailFormat(emailInput.value)) {
    showError('Please enter a valid email address.');
  }
});

const response = await fetch('https://app.lettr.com/api/emails', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    from: 'noreply@yourdomain.com',
    to: 'new-subscriber@example.com',
    subject: 'Confirm your subscription',
    html: '<p>Click the link below to confirm your email address:</p><a href="https://yourdomain.com/confirm?token=abc123">Confirm Subscription</a>',
  }),
});

app.post('/webhooks/lettr', (req, res) => {
  const event = req.body;

  if (event.type === 'email.bounced') {
    const { to, bounceType } = event.data;

    if (bounceType === 'hard') {
      // Permanently remove from all mailing lists
      removeFromAllLists(to);
      logBounce(to, 'hard', event.data.reason);
    }

    if (bounceType === 'soft') {
      // Track soft bounces — remove after 3 consecutive failures
      incrementSoftBounceCount(to);
      const count = getSoftBounceCount(to);

      if (count >= 3) {
        removeFromAllLists(to);
        logBounce(to, 'soft_permanent', event.data.reason);
      }
    }
  }

  res.sendStatus(200);
});

app.post('/webhooks/lettr', (req, res) => {
  const event = req.body;

  if (event.type === 'email.complained') {
    const { to } = event.data;

    // Remove from all lists immediately — do not email this person again
    removeFromAllLists(to);
    addToInternalBlocklist(to);

    // Log for analysis — high complaint rates need investigation
    logComplaint(to, event.data);
  }

  res.sendStatus(200);
});

async function applySunsetPolicy() {
  const inactiveWindow = 270; // days (9 months)
  const cutoffDate = new Date(Date.now() - inactiveWindow * 24 * 60 * 60 * 1000);

  const inactiveSubscribers = await db.subscribers.findMany({
    where: {
      lastEngagement: { lt: cutoffDate },
      status: 'active',
    },
  });

  for (const subscriber of inactiveSubscribers) {
    await db.subscribers.update({
      where: { id: subscriber.id },
      data: { status: 'sunset_removed' },
    });
  }

  console.log(`Sunset policy removed ${inactiveSubscribers.length} inactive subscribers.`);
}