Email Metrics After Mail Privacy Protection

Since Apple introduced Mail Privacy Protection (MPP) in September 2021, the open rate has stopped meaning what most marketers think it means.¹ MPP runs in Apple Mail on iPhones, iPads, and Macs on current software, and it was built specifically to keep senders from learning when, where, and whether someone read their mail. A program that still steers by opens is steering by a number Apple is generating on the subscriber's behalf.

MPP hides the reader behind Apple's servers

MPP does two things that matter to senders. First, it hides the recipient's IP address, so a sender can't use it to work out the recipient's location or tie their email activity to other online behavior. Second, Apple fetches remote content, including images and tracking pixels, through its own proxy servers, generally in the background and not when the person actually reads the message. The tracking pixel still fires, and it may still be attributed to the right subscriber, but the request comes from Apple, at a time Apple chose, from an IP address that says nothing about the reader.

The result is opens that look real and aren't.

Opens are inflated, and everything built on them broke

Open rates used to be the default measure of campaign performance. For MPP users, they now report that Apple's servers retrieved the content. They are inflated and unreliable, and the useful signal moves to clicks and conversions.

Anything that depended on opens inherits the same problem. Segments built on open behavior lose their meaning, and so does send-time optimization, which relies on knowing when someone opened. Purchase history, website behavior, and preferences subscribers tell you themselves are better inputs now. Subject line tests scored on opens are compromised for the same reason, so score them on clicks instead.

The programs that adapt rely on what subscribers actually do

Content worth clicking matters more when clicks are your signal. Personalization should come from behavior and preferences you can trust, not from open data you can't. Preheader text deserves more attention than it usually gets because it helps persuade someone to engage at all.

The privacy shift that produced MPP also makes it essential to get permission right. Ask for explicit consent rather than assuming it. Confirmed opt-in gives you a list of people who actually wanted the mail, and that list produces engagement data you can believe.

And bring your Chief Privacy Officer into the conversation. A good CPO does more than say "no." They can help you understand where privacy expectations are headed and build a marketing program that is designed for them instead of being surprised by them.

MPP is one example of a broader shift toward user privacy, and it will not be the last. The marketers who come out ahead stop trying to recover the old open rate and start measuring what subscribers do on purpose.