What it means
A tracking pixel is a remote image in an email that can reveal information about when a client loaded a message. Apple Mail Privacy Protection reduces this signal by obscuring IP and open activity. Clicking a link, however, actively opens a website that can collect its own information.
A real-world example
A newsletter sender cannot reliably infer when a protected Mail user opened the email, but the sender's website can still observe a visit if the reader taps its offer link.
What to do
Enable Mail Privacy Protection where available and inspect the destination of unexpected links before following them. Treat attached files as another separate decision.
The distinction that matters
Protecting remote image retrieval does not anonymize all email behavior. Apple says the feature does not extend to links or attachments, and other mail apps can use different privacy settings. The sender may know when you reply, regardless of image privacy.
Apple's Mail privacy explanation
