Open tracking is technology used by ESPs, like EmailOctopus, to calculate open rates. It works by adding a small 1px image, which is unique to the subscriber, at the bottom of the email. When the unique image loads, the ESP makes the assumption that the email has been opened by the recipient. This is then reflected in email campaign reports as an open.
As a technology it has always been unreliable. Some people open emails with images turned off while some ad blockers block 1px images. In these cases, emails might be opened without the ESP being able to register that the open took place.
Open tracking has largely been useful in providing insight into the performance of an email, at least in terms of opens. But with Mail Privacy Protection, Apple Mail (on Mac and iOS) will now load those 1px images in an email as soon as it’s received. Even if the user hasn’t physically opened the email themselves.
As a result, emails sent to an iOS 15 device (or a Mac running Monterey) using Apple Mail, will show as an open. With a few caveats.
Firstly, MPP only pre-fetches images when the device is plugged in to a power source.
Secondly, MPP only pre-fetches images when the device is connected to WiFi.