Open Rate
Open Rate is the percentage of email recipients who open a sent message — a basic engagement metric, though increasingly unreliable since Apple Mail Privacy Protection (2021) inflates open counts via prefetching.
What is Open Rate?
Open Rate was once the cleanest email engagement metric — the recipient explicitly opened, so the subject line worked and the message got past the spam filter. Apple Mail Privacy Protection changed that: Apple Mail clients now prefetch messages, registering an open whether the user opened or not. The result is inflated open rates that don't reliably reflect engagement. Modern email programs increasingly de-emphasize Open Rate in favor of reply rate, click-through, and meetings booked. Open Rate still matters as a deliverability proxy — if it craters, something's wrong with deliverability.
Why it matters
- Once-clean engagement metric, now unreliable due to mail-client prefetching.
- Still useful as a deliverability canary — sudden drops signal an inbox-placement problem.
- De-emphasized in favor of reply rate and downstream conversion metrics.
Use cases
- Deliverability monitoring. Open-rate drops as the first signal of inbox-placement issues.
- Subject-line A/B testing. Still useful where the test holds other variables constant.
- Historical comparison. Comparing open rates over time, controlling for client mix.
How turgo helps
turgo tracks Open Rate alongside reply rate, click-through, and meeting-booked — so the open metric is contextualized rather than used in isolation.
See turgo in action →
