List Management

Maintaining clean email lists through suppression, hygiene, and data retention.

Suppression Lists

A suppression list prevents sending to addresses that should never receive email.

What to Suppress

Reason	Action	Can Unsuppress?
Hard bounce	Add immediately	No (address invalid)
Complaint (spam)	Add immediately	No (legal requirement)
Unsubscribe	Add immediately	Only if user re-subscribes
Soft bounce (3x)	Add after threshold	Yes, after 30-90 days
Manual removal	Add on request	Only if user requests

Implementation

// Suppression list schema
interface SuppressionEntry {
  email: string;
  reason: 'hard_bounce' | 'complaint' | 'unsubscribe' | 'soft_bounce' | 'manual';
  created_at: Date;
  source_email_id?: string; // Which email triggered this
}

// Check before every send
async function canSendTo(email: string): Promise<boolean> {
  const suppressed = await db.suppressions.findOne({ email });
  return !suppressed;
}

// Add to suppression list
async function suppressEmail(email: string, reason: string, sourceId?: string) {
  await db.suppressions.upsert({
    email: email.toLowerCase(),
    reason,
    created_at: new Date(),
    source_email_id: sourceId,
  });
}

Pre-Send Check

Always check suppression before sending:

async function sendEmail(to: string, emailData: EmailData) {
  if (!await canSendTo(to)) {
    console.log(`Skipping suppressed email: ${to}`);
    return { skipped: true, reason: 'suppressed' };
  }

  return await resend.emails.send({ to, ...emailData });
}

List Hygiene

Regular maintenance to keep lists healthy.

Automated Cleanup

Task	Frequency	Action
Remove hard bounces	Real-time (via webhook)	Immediate suppression
Remove complaints	Real-time (via webhook)	Immediate suppression
Process unsubscribes	Real-time	Remove from marketing lists
Review soft bounces	Daily	Suppress after 3 failures
Remove inactive	Monthly	Re-engagement → remove

Re-engagement Campaigns

Before removing inactive subscribers:

Identify inactive: No opens/clicks in 90-180 days
Send re-engagement: "We miss you" or "Still interested?"
Wait 14-30 days for response
Remove non-responders from active lists

async function runReengagement() {
  const inactive = await getInactiveSubscribers(90); // 90 days

  for (const subscriber of inactive) {
    if (!subscriber.reengagement_sent) {
      await sendReengagementEmail(subscriber);
      await markReengagementSent(subscriber.email);
    } else if (daysSince(subscriber.reengagement_sent) > 30) {
      await removeFromMarketingLists(subscriber.email);
    }
  }
}

Data Retention

Email Logs

Data Type	Recommended Retention	Notes
Send attempts	90 days	Debugging, analytics
Delivery status	90 days	Compliance, reporting
Bounce/complaint events	3 years	Required for CASL
Suppression list	Indefinite	Never delete
Email content	30 days	Storage costs
Consent records	3 years after expiry	Legal requirement

Retention Policy Implementation

// Daily cleanup job
async function cleanupOldData() {
  const now = new Date();

  // Delete old email logs (keep 90 days)
  await db.emailLogs.deleteMany({
    created_at: { $lt: subDays(now, 90) }
  });

  // Delete old email content (keep 30 days)
  await db.emailContent.deleteMany({
    created_at: { $lt: subDays(now, 30) }
  });

  // Never delete: suppressions, consent records
}

Metrics to Monitor

Metric	Target	Alert Threshold
Bounce rate	<2%	>5%
Complaint rate	<0.1%	>0.2%
Suppression list growth	Stable	Sudden spike
List churn	<2%/month	>5%/month

Transactional vs Marketing Lists

Keep separate:

Transactional: Can send to anyone with account relationship
Marketing: Only opted-in subscribers

Suppression applies to both: Hard bounces and complaints suppress across all email types.

Unsubscribe is marketing-only: User unsubscribing from marketing can still receive transactional emails (password resets, order confirmations).

Webhooks & Events - Receive bounce/complaint notifications
Deliverability - How list hygiene affects sender reputation
Compliance - Legal requirements for data retention

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