How does Apple’s MPP confuse engagement-based filters?

Apple Mail Privacy Protection (MPP), introduced in 2021, pre-loads email content including tracking pixels regardless of whether users actually open messages. This has significant implications for engagement measurement.

MPP causes inflated open rates for Apple Mail users because the tracking pixel fires whether or not the recipient reads the message. Senders cannot distinguish genuine opens from Apple's pre-loading.

For filtering, this creates measurement noise. Open data from Apple Mail users becomes unreliable as an engagement signal. Filters must weight this data differently or rely more heavily on other signals.

Click data remains reliable because MPP does not click links. Senders and filters can still use clicks as genuine engagement indicators.

The impact varies. Filters that heavily weighted opens may have adjusted their models. Senders must look beyond opens to assess true engagement.

MPP obscured one signal in the engagement constellation. Smart navigators learned to read the remaining stars.