What is Apple Mail Privacy Protection (MPP)?

You send a campaign, check your stats a few hours later, and see a 60% open rate. A year earlier that number was hovering around 25%. Nothing about your emails changed. What changed was iOS 15, which shipped in September 2021 with a feature called Mail Privacy Protection that fundamentally changed how email open tracking works for a large share of your audience.

Apple Mail Privacy Protection, usually shortened to MPP, is a privacy feature built into Apple's Mail app on iPhone, iPad, and Mac. When someone enables it (which Apple prompts users to do on first launch after the iOS 15 update), Apple's servers pre-fetch and cache all images in incoming emails, including your tracking pixel, before the email even reaches the reader's device. Your ESP records an "open" the moment Apple's proxy loads the pixel, regardless of whether the person actually looked at the email. Since Apple Mail users make up a significant share of most consumer email audiences (often 50% or more in B2C programs), this inflated open rate reporting across the industry essentially overnight.

The practical effect is that open rates are no longer a reliable engagement signal for a large portion of your list. An "open" from an Apple Mail user tells you that Apple's servers fetched your email. It doesn't tell you whether the person read it, ignored it, or deleted it immediately. If you're using open rate as a threshold for re-engagement campaigns (like "anyone who hasn't opened in 90 days"), your segments are now misclassified for every subscriber using Apple Mail with MPP enabled. People it marks as "active openers" may have been completely disengaged for months.

MPP also affects IP-based location data. Apple routes all image requests through its own proxy servers, masking the reader's real IP address. Geolocation-based segmentation (like send-time optimization by timezone, or country-level targeting) becomes unreliable for Apple Mail users, since the IP your ESP records belongs to Apple, not your subscriber. Both your open rate and your location data for this segment are compromised at the same time.

The right response is to shift your engagement definitions away from opens and toward clicks. Instead of "hasn't opened in 90 days," use "hasn't clicked in 90 days" as your re-engagement threshold. Clicks are human-initiated actions that Apple doesn't pre-fetch on anyone's behalf. Most ESPs now let you segment by click activity directly, and click-based segmentation is more meaningful than open-based anyway. Start there before you overhaul anything else.