Transactional Email Best Practices for SaaS Apps

Why Transactional Emails Matter

Transactional emails — password resets, order confirmations, welcome emails — have the highest open rates of any email type (80%+ average). They're critical for user experience and retention.

If a user can't reset their password because your email didn't arrive, you lose that user forever.

Infrastructure Decisions

Dedicated Domain

Never send transactional emails from your marketing domain. Use a subdomain:

• mail.yourapp.com for transactional
• news.yourapp.com for marketing

This protects your transactional reputation if marketing emails cause spam complaints.

API vs SMTP

Recommendation: Use REST API for new applications. Use SMTP only for legacy systems.

Essential Transactional Emails

Every SaaS app should have these:

• Welcome email — Sent immediately after signup
• Email verification — Confirm the address is real
• Password reset — Time-limited, secure tokens
• Invoice/receipt — After payment
• Usage alerts — Approaching plan limits

Template Best Practices

• Keep it simple — Transactional emails should be functional, not flashy
• One clear CTA — Each email should have one primary action
• Mobile responsive — 60%+ of emails are opened on mobile
• Consistent branding — Same logo, colors, and footer on every email
• Plain text fallback — Always include a text version

Error Handling

async function sendEmailWithRetry(params: EmailParams, retries = 3) {
  for (let i = 0; i < retries; i++) {
    try {
      const { data, error } = await unosend.emails.send(params);
      if (error) throw new Error(error.message);
      return data;
    } catch (err) {
      if (i === retries - 1) throw err;
      await new Promise(r => setTimeout(r, 1000 * Math.pow(2, i)));
    }
  }
}

Key points:

• Retry with exponential backoff — Don't hammer the API on failure
• Log failures — Track which emails fail and why
• Alert on critical failures — Password resets and verifications must succeed
• Queue non-urgent emails — Notifications can be slightly delayed

Monitoring

Set up webhooks to track:

• Delivered — Email accepted by recipient's server
• Opened — Recipient opened the email (pixel tracking)
• Clicked — Recipient clicked a link
• Bounced — Email rejected (remove from list!)
• Complained — Marked as spam (stop emailing this person!)

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

  switch (event.type) {
    case 'email.bounced':
      suppressEmail(event.data.to);
      break;
    case 'email.complained':
      suppressEmail(event.data.to);
      alertTeam(event.data);
      break;
  }

  res.sendStatus(200);
});

Quick Setup Guide

• Sign up for an email API (Unosend gives 5,000 free/month)
• Verify your sending domain (SPF + DKIM)
• Build your core email templates
• Implement send with retry logic
• Set up webhook handlers for bounces/complaints
• Monitor deliverability in your dashboard