What exactly was announced?
Here’s what it says on Apple’s website:
In the Mail app, Mail Privacy Protection stops senders from using invisible pixels to collect information about the user. The new feature helps users prevent senders from knowing when they open an email, and masks their IP address so it can’t be linked to other online activity or used to determine their location.
The “invisible pixels” mentioned here are also known as tracking pixels — tiny images embedded in an email that load when a recipient opens that email. That delivers a signal to the sender that tells them the email has been opened, and it’s how services like Revue calculate what the Open Rate of your newsletter issue was.
We don’t have all of the information yet on how this will work, but under the new design, Apple Mail will effectively indicate that an email was opened by the recipient as soon as it lands in their inbox, whether or not they actually opened it.