Apple iOS 15 Mail Privacy Protection Open Rate Trends

Apple’s Mail Privacy Protection (MPP) rollout in iOS 15 has caused fascinating changes in open rate metrics. The most interesting of which is the change in behavior of when we see opens being detected.

Let’s dive into a few charts using data from hundreds of millions of delivered messages.

Apple Mail open trends by a percentage of total mails sent after Apple's iOS 15 Mail Privacy Protection roll out (MPP)
Apple Mail opens by a percentage of total mail sent

Below you’ll see the raw volume trends of user opens as Apple iOS 15 is adopted on an hourly basis.

Raw email opens by hour as Apple iOS 15 is adopted
Raw opens by hour as Apple iOS 15 is adopted.

More Night Time Readers?

Look closely and you’ll see the peaks and valleys are different on older iOS versions vs. Apple’s new MPP proxy in iOS 15. Putting proxied iOS 15 traffic on the right axis highlights the trend.

Why does this happen?

iOS 15 only does the image caching in the background when devices are plugged in and on WIFI. What happens in the evening? People go to sleep and charge their phones.

Nighttime opens are increasing as iOS 15 downloads images while your device is charging overnight.
Nighttime opens are increasing as iOS 15 downloads images while your device charges on your bedside table.

Nighttime Dominates

When you aggregate all opens for each type over a 24 hour period and look at the percentage of opens that happen in any given hour during that day, the trend becomes very clear. The overwhelming majority of opens from iOS 15 are detected in the evening, not from human activity but from caching while your phone charges.

While your iPhone charges it “opens” and downloads each of the images in the messages you’ve received but haven’t yet looked at. This caches the image and stores it for later so you can view the message faster. This creates an artificial open, but one that’s still seen in the metrics.

Nighttime  image download trends
Nighttime image downloading trends.

Global Open Rates

The iOS 15 MPP caching is already having a slight impact on global open rates in the past few days. Nothing dramatic, but it does show up on graphs.

AWeber Global open rates as iOS 15 rolls out
Global open rates as iOS 15 rolls out.

iCloud Open Rates

That impact is clearer when you drill into opens for an audience that’s much more likely to be viewing their email exclusively on Apple devices. Open rates have shown a growing trend but not one that yet impacts how most marketers need to think about using open rates. open rate trends with an upward trajectory after iOS 15. opens trend up

Apple’s Influence on Global Opens

I expect the volume of older iOS traffic to continue gradually dropping off, but it’s obvious when you look at the wider email ecosystem that Google still dominates with Gmail proxied requests. The volume from older pre iOS 15 devices will continue to drop, and the slice of red from iOS 15 devices will grow with the automated image downloading.

Global opens by browser type

I wrote about Apple iOS 15’s Mail Privacy Protection in June and what I wrote then still holds true. Apple’s changes

  • make open rate tracking less reliable, but still gives you useful information.
  • hides users IP addresses behind a proxy service.
  • has zero impact on how people read and view your emails.
  • gives Apple a TON of data on their users that they didn’t have before.

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