Apple introduced Mail Privacy Protection in September 2021, and email open rates have not meant the same thing since. If you're still reporting open rate as your primary success metric without an asterisk attached, the number on your dashboard is telling you less than you think.

What MPP actually does

When someone with MPP enabled receives an email, Apple's own servers download the entire message, including the tracking pixel, automatically and immediately, regardless of whether the person ever looks at it. Your email platform records that pixel download as an open. The subscriber may never actually see the email, and it registers as opened anyway.

The scale of this is significant. Apple Mail accounts for a large share of global email opens, and industry estimates put the resulting inflation at somewhere between 15 and 20 percentage points above genuine human engagement, though the exact figure varies by list composition and how iOS-heavy your audience is.

IMPORTANT

If your dashboard shows a 42% open rate, your real, human open rate could plausibly be closer to 25%. The gap is not a flaw in your programme. It's a measurement artefact affecting every sender with any meaningful Apple Mail audience.

Why this matters beyond the vanity of the number

It's not just that the number looks better than reality. MPP corrupts anything built on top of open data: A/B tests that use opens to pick a winning subject line, send-time optimisation trained on when opens happen, and segmentation that defines 'engaged' based on who opened recently. All of these are working from partially fictional data now.

What still works as a signal

Clicks remain genuine. MPP intercepts the tracking pixel, but it doesn't fabricate a click, because a click requires the recipient to actually interact with a link. This makes click rate, and specifically click-to-open rate, a far more trustworthy indicator of real engagement than open rate alone.

The two things open rate is still useful for

Open rate isn't worthless, it's just narrower in what it can tell you than it used to be. It's still useful for spotting a sudden cliff: if your open rate drops ten or more points overnight, something changed in deliverability, even if the absolute number was never accurate to begin with. It's also still useful for relative comparison between two campaigns sent to a similar audience on the same day, since both carry roughly the same MPP inflation, so the difference between them likely reflects a real subject line or timing effect.

What to build your reporting around instead

Click-through rate and click-to-open rate should move to the centre of your reporting, since both are built on genuine interaction rather than a pre-fetched pixel. Conversion rate and revenue per recipient go further still, tying performance directly to what the business actually cares about. For list segmentation, defining 'engaged' by clicks and site activity within a rolling window, rather than opens, gives you a segment that's actually behaving the way the label suggests.

How Mail Blaze approaches this

This is exactly why comparative filters exist: rather than reading a single open rate in isolation, you can compare campaigns against each other and against your own account's baseline, which controls for the MPP inflation affecting every send roughly equally. The Subscriber Score is built on a broader mix of engagement signals too, not open data alone, specifically because open rate has become an unreliable single source of truth.

Mail Blaze is an email marketing platform built for teams who want more from email. Comparative filters and Subscriber Score exist because engagement is a relationship, not a single inflated number on a dashboard.

Frequently Asked Questions

What is Apple Mail Privacy Protection?

A privacy feature, introduced in September 2021, that has Apple's own servers pre-load email content and tracking pixels automatically, regardless of whether the recipient actually opens the message.

How much does MPP inflate open rates?

Estimates commonly range from 15 to 20 percentage points above genuine human engagement, depending on how much of your list uses Apple Mail.

What should I track instead of open rate?

Click-through rate, click-to-open rate, conversion rate, and revenue per recipient are all built on genuine interaction rather than a pre-fetched pixel.

Is open rate completely useless now?

No. It's still useful for spotting sudden deliverability drops and for relative comparisons between similar campaigns, just not as an absolute measure of engagement.