/ Glossary — List & Compliance
What is Mail Privacy Protection?
Apple's privacy feature that pre-loads message images on its own servers and hides recipient IPs — quietly breaking open tracking for a huge share of email. Here's what it changes.
/ Definition
Mail Privacy Protection, or MPP, is a feature Apple introduced for the Apple Mail app that protects recipient privacy in two main ways: it pre-loads message content, including images, through Apple's own servers rather than the recipient's device, and it masks the recipient's IP address. For senders, the consequential part is the image pre-loading, because it breaks the tracking that email metrics have long relied on.
The tracking pixel that measures opens depends on an image loading when a human views a message. MPP loads that pixel automatically for Apple Mail users whether or not they open the mail, registering false opens and inflating open rates. Because Apple Mail is a large share of the market, MPP has made open rate an unreliable metric across the board.
/ In practice
How MPP changes your metrics
The direct casualty is open rate. Since MPP pre-loads the tracking pixel for affected users regardless of whether they read the message, those users count as opens unconditionally — so aggregate open rates rise in a way that reflects Apple's servers, not human behavior. The inflation isn't uniform: it scales with how many of your recipients use Apple Mail, so two senders with identical real engagement can show very different open rates. IP masking also affects any location or device data you inferred from the open, removing another signal. The net effect is that open-based measurement and automation built on it have become unreliable.
What to do about it
The practical response is to shift the metrics you depend on away from opens toward actions that reflect genuine intent: clicks, replies, conversions, and the absence of complaints or unsubscribes. Engagement-based decisions — like which subscribers to target or sunset — should lean on these harder signals rather than opens. For deliverability specifically, the metrics that actually matter, like complaint rate, bounce rate, and real inbox placement, are unaffected by MPP. Treating open rate as a rough directional signal rather than a precise number is the adjustment MPP forces, and it's a healthier basis for measurement anyway.
/ Related terms
MPP broke open tracking. We measure what it can't touch.
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