Email Open Rate
Email open rate is the percentage of delivered emails that recipients open, calculated by dividing unique opens by the number of successfully delivered emails and multiplying by 100.
What Is Email Open Rate?
On the surface, open rate looks simple: people either open your email or they don't. But the metric has become considerably more complicated since Apple introduced Mail Privacy Protection (MPP) in September 2021. MPP pre-fetches email content — including tracking pixels — before a user ever touches their inbox, which means opens get recorded even when no human actually read a word. For senders with large chunks of their audience on Apple Mail, reported open rates can be inflated by anywhere from 10 to 40 percentage points. That's not a rounding error. It fundamentally changes what the number means. Despite this, open rate remains one of the most widely watched metrics in email marketing, and it's not without value. Trends still matter — a sudden drop in open rate is a reliable signal that something has gone wrong, whether that's a deliverability problem, a subject line that missed badly, or a disengaged list that's overdue for cleaning. Benchmarks vary significantly by industry and list size, but for newsletters a healthy open rate typically sits somewhere between 30% and 50% for engaged audiences. Anything consistently below 20% warrants serious attention.
Why It Matters for Newsletters
For newsletter creators, open rate is both a health check and a feedback loop. It tells you, broadly, whether your subject lines are doing their job and whether your audience still looks forward to hearing from you. A declining open rate is often the first visible symptom of deeper problems — list fatigue, poor segmentation, or emails landing in the promotions tab instead of the inbox. Catch it early and you can course-correct. Ignore it and you risk damaging your sender reputation as inbox providers interpret low engagement as a signal to route future emails away from the primary inbox. The key is not to treat open rate as gospel. Use it directionally. Compare it against your own historical baseline rather than obsessing over industry averages. And pair it with click-through rate and click-to-open rate to get a fuller picture of whether your content is actually landing — because an 'open' that MPP fabricated tells you nothing about whether your readers are genuinely engaged.
Best Practices
- Track open rate trends over time rather than fixating on individual sends — a consistent pattern tells you far more than a single data point.
- Segment your open rate reporting by email client where possible, so you can account for the distortion caused by Apple Mail Privacy Protection.
- Use click-to-open rate alongside open rate to gauge true engagement — it filters out ghost opens and shows whether the people who did open actually found the content worth clicking.
- Test subject lines and preheader text rigorously; these two elements together are almost entirely responsible for whether an open happens at all.
- Treat a sustained open rate below 20% as an urgent prompt to run a re-engagement campaign and prune inactive subscribers before your sender reputation takes a hit.
How Aldus Handles This
Aldus surfaces open rate data in context — showing you trends, flagging anomalies, and helping you understand what's signal versus noise in a post-MPP world. Rather than just displaying a raw percentage, Aldus pairs open rate with click and engagement data so you can make decisions based on how your audience is actually behaving, not just what the tracking pixel recorded.