Why is this a big deal, again?
Back in June, Apple announced this:
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.
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.
After that first announcement, most (including us) thought that would mean all subscribers using Apple Mail will register as having opened your email, skewing Open Rate data. Here’s what I wrote in June:
If this works as expected, […] every reader on your list who uses Apple Mail will count as an ‘Open’, so you would see your Open Rates go up — even if fewer people actually read your emails.