Once your transactional emails are sending, it’s important to keep an eye on your high-level metrics. Tracking the right metrics ensures your critical communications are reaching users and driving the desired behaviors.
Important delivery metrics
Delivery Rate
Measures the percentage of emails accepted by receiving mail servers. This should be your north star metric for transactional email. Typically, you want to ensure you have a 98-99% delivery rate – anything below 98% may indicate issues with your sending infrastructure, domain reputation, or message content. Remember, even small drops can lead to missed password resets, failed confirmations, or churn.
Bounce Rate
Measures how many emails aren’t making it to the intended inbox, split between hard bounces (invalid addresses) and soft bounces (temporary failures). High bounce rates (>0.5% for hard bounces, >1.5% for soft bounces) indicate data quality issues or deliverability problems. Most ESPs will flag or throttle your account if bounce rates exceed these thresholds consistently.
Time to Inbox
Measures how long between triggering an event and the email landing in the recipient's inbox. This metric is critical for time-sensitive emails like password resets or 2FA codes, so if you're seeing delays in the 30+ second range, it’s a sign of upstream processing lag, queueing issues, or ESP throttling that should be investigated.
Important engagement metrics
Open Rate
Measures what percentage of your audience opens an email. While less critical than for marketing emails, abnormally low open rates (anywhere below 60%) can indicate deliverability issues or subject line problems. Keep in mind: open rates are increasingly unreliable due to Apple Mail Privacy Protection and similar features, so track clicks or time-to-action for a more accurate signal when possible.
Click Rate
Measures what percentage of your audience clicks an email. This metric is particularly important for emails with critical CTAs (password resets, order confirmations, account verifications).
Completion Rate
For transactional emails driving specific actions, it’s helpful to track whether users complete the intended task (reset password, verify email, review order). Benchmarks for this metric vary widely depending on the audience and task.
Unsubscribe Rate
Measures what percentage of your audience unsubscribes from your emails. For transactional emails, high unsubscribe rates (>0.1%) likely indicate content or frequency problems and can hurt your sender reputation.
Important technical health metrics
Spam Complaint Rate
Measures the percentage of users reporting your emails as spam. This is critical to monitor, as vendors like Gmail start to penalize senders at rates as low as 0.1%, which can permanently damage your sender reputation and future deliverability.
Authentication Pass Rate
Measures the percentage of emails passing SPF, DKIM, and DMARC checks. Low pass rates will directly impact deliverability.
Provider Error Rates
Track failures by ESP (rate limits, API errors, service outages) to identify reliability issues.
Template Render Failures
Monitor when personalization or dynamic content fails to render correctly.
Important business impact metrics
Activation Rate
For onboarding emails, what percentage of users complete account setup after receiving verification emails?
Recovery Rate
For password reset flows, how many users successfully reset their password after requesting?
Support Ticket Rate
It can be helpful to track the number of support tickets related to "didn't receive email" issues per thousand emails sent.
Revenue Attribution
For order confirmations and shipping notifications, track downstream actions like repeat purchases or review submissions.
Remember: the goal of transactional emails isn't to optimize for opens and clicks like marketing emails. Instead, focus on reliable delivery, timely arrival, and successful task completion. If users are completing their intended actions without contacting support, your transactional email system is working.
Ship transactional email that works
The best transactional email system is invisible and works seamlessly in the background. With the right setup, there should be no support tickets about missing emails, no engineering time lost to deliverability mysteries, and no bad sentiment from poor user experiences–just messages that arrive instantly, exactly when users need them.
We covered a lot in this guide, but here's some of the most important takeaways:
- Use an ESP.
- Don’t skip authentication.
- Set up templates, partials, and localization early.
- Monitor important metrics and adjust accordingly.
- When complexity grows, invest in a notification infrastructure platform.
Ready to skip the complexity entirely? Try Knock for free and start sending better transactional notifications in minutes, not months.