How does MPP (Mail Privacy Protection) affect tracking?
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In September 2021, Apple shipped iOS 15 with a feature called Mail Privacy Protection. If you were watching your open rates at the time, you probably noticed them jump overnight. Not because more people were reading your emails. Because Apple started opening them for everyone.
Here's what Mail Privacy Protection (MPP) does: when a recipient with the setting enabled opens your email in Apple Mail (on iPhone, iPad, or Mac), Apple's servers pre-fetch all remote content in the message, including tracking pixels, before passing it to the user. This happens whether or not the person actually reads the email. The open gets logged, but it didn't come from the real human. It came from Apple's proxy.
The consequences for open rate tracking are significant. Any recipient using Apple Mail with MPP enabled will register as an open in your stats, regardless of real engagement. For some senders, Apple Mail represents 40-60% of their audience. That's a lot of ghost opens inflating the numbers.
Beyond open inflation, MPP masks IP addresses and location data. The image request comes from Apple's proxy, not the recipient's device. So geo-targeting and device data based on pixel tracking become unreliable for Apple Mail users too.
The practical response is to shift away from open rates as a primary engagement metric. Click tracking still works accurately (clicks require a real human to act). Revenue per email, conversion rate, and reply rate are all better signals than opens in a post-MPP world. You can also try to detect MPP-triggered opens by looking at batch-timing patterns in your data, but that's an imperfect science. Better to just design your measurement strategy around clicks and conversions from the start.
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