A large share of your recipients open every email the instant it arrives, and none of them touched it. What Apple Mail's privacy setting does to a read receipt.

What the setting actually does

The mail app in question added, a few years ago, a privacy protection that is on by default and that most people simply left on without thinking about it. When it is active, incoming mail is routed so that all of its remote images, the tracking pixel included, are fetched ahead of time by the provider's own servers, not by the person's device when they read. The stated goal is exactly to defeat open tracking: if the pixel is always fetched, on delivery, from a neutral server, then an open no longer reveals whether or when the recipient read, or where they were. It works as intended. It turns the pixel from a signal about a person into a signal about the arrival of mail.

Why that breaks the receipt so completely

Notice how total this is. Other things that fool a pixel are occasional: a scanner here, a preview pane there. This is systematic. For every recipient who has the setting on, every message you send opens once, almost immediately, no matter what they do next. They can read it, delete it unread, or never look at all, and your receipt says the same thing: opened, seconds after you sent it. So for that whole group of people, the open is not a weak signal, it is no signal. It fires identically for the attentive reader and the one who never saw it. And you usually cannot tell from your side which recipients are in that group, because it is their setting, invisible to you.

The scale is the part people underestimate

It would be a footnote if it were rare. It is not. A very large share of personal email is read in that app, on phones and on laptops, and the protection is on by default, so the share of your recipients it covers is not small. This is why people who watch open rates on ordinary mail sometimes see them climb toward numbers that would be impossible if they meant real reads. The number did not improve. A big slice of it turned into automatic fetches that happen whether or not anyone reads. An open rate quietly stopped measuring opens for a large part of the audience, and nobody sent a notice that it had changed.

How to read receipts honestly in this world

The move is not to throw the receipt away, it is to demote what a single early open means and to lean on the shapes it cannot fake. An open that arrives seconds after you send, especially at an odd hour, is most likely an automatic fetch and deserves little weight on its own. A reply is still a reply and still outranks everything. And the receipt is still useful in the cases the protection does not touch: recipients who use other mail apps, and above all the human signals, someone opening, then replying, then acting. Treat a lone instant open as "delivered, and maybe fetched automatically", not as "read". Treat the presence of a real back and forth as the thing that actually tells you you were read. The pixel became a weaker instrument for a big group of people, and the honest response is to know that and to stop asking it for a certainty it can no longer give.

The general shape

When a measurement has been quietly redefined by a change you did not make and were not told about, the dangerous move is to keep reading it by its old meaning. A default privacy setting redefined what an open is for a large share of email, from "a person looked" to "mail arrived". Nothing on your screen marks which receipts were redefined, so the only defense is to carry the knowledge that the redefinition happened and to weight the signal accordingly. Know what your number counts now, not what it counted when you first learned to trust it.

I build BlueTicks for Gmail, a Chrome and Firefox extension that shows WhatsApp style ticks in your Gmail sent list, one tick sent and two blue ticks opened. For recipients whose mail app pre-fetches images, an open can fire on delivery, so I would rather you read the ticks as a strong hint backed up by replies than as proof. It costs 4 dollars a year, and the free tier covers 30 emails a month. You can find it at blueticks.io.