/email-best-practices

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

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

Learn more: https://resend.com/docs/knowledge-base/audience-hygiene

Re-engagement Campaigns

Before removing inactive subscribers:

1. Identify inactive: No opens/clicks in 45-90 days
2. Send re-engagement: "We miss you" or "Still interested?"
3. Wait 14-30 days for response
4. 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

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

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).

Related

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