What’s the risk of overinterpreting open data (MPP distortion)?

Your open rate jumps to 60%. Exciting, right? Maybe not. If a big chunk of your list reads email on Apple Mail, a lot of those "opens" probably never happened.

Mail Privacy Protection (MPP), launched by Apple in 2021, pre-fetches your tracking pixel before the reader even looks at the email. Your ESP records an open. The reader may have deleted it without a second glance. You'd never know the difference.

The danger isn't just an inflated number. It's what you do with that number. When open rates look healthy, you might miss that real engagement is quietly dropping. You might keep sending to a list that's gone cold. You might make content decisions based on a signal that has nothing to do with actual human interest.

How to spot MPP distortion in your data

The clearest tell is a sudden spike in opens right after Apple announced MPP in September 2021. If your open rate jumped significantly around that time and never came back down, that's not a coincidence.

Another signal to watch for is unusual open timing. Real humans open emails at scattered times throughout the day. MPP pre-fetching tends to cluster opens in a tight window right after delivery. If your ESP shows a flood of opens in the first few minutes across a huge portion of your list, that's almost certainly automated.

You can also segment by email client. Most ESPs let you filter engagement data by client type. Pull your open rates for Apple Mail users separately and compare them to your Gmail or Outlook segments. If Apple Mail opens are dramatically higher with no other explanation, MPP is likely inflating the picture.

What to measure instead

Click rates are your best friend here. MPP doesn't click links. A real person has to do that. So clicks tell you far more about genuine engagement than opens ever did (even before MPP muddied the water).

Downstream conversions matter too. Did people visit your site after the send? Did they buy something? Did they reply? These actions reflect real interest in a way that a pre-fetched pixel never can.

For list health, track engagement decay over time using click and conversion trends rather than open trends. If those metrics are falling, you have a real problem regardless of what the open rate says.

And when you do reference opens, use relative comparisons. Compare open rates campaign to campaign within the same audience segment rather than treating the absolute number as meaningful. Trends matter. Totals, at this point, are mostly noise.

If you want to check which signals in your setup are worth trusting, our free Email Header Analyzer can help you dig into what's actually happening at the delivery level. Or if you're seeing something weird and want a second pair of eyes, the SOS hotline is free.