In the Mail app, Mail Privacy Protection stops senders from using invisible tracking pixels to collect information about you. This new feature helps users prevent senders from knowing when they open an email. It also masks your IP address so it can’t be linked to other online activity or used to determine your location.
iOS 15 you can now block these tracking pixels.
Here's how to turn this feature on in iOS:
Go to Settings > Mail.
Tap Privacy Protection
Toggle "Protect Mail Activity" on
More information: Apple advances its privacy leadership with iOS 15...