The advice not to load images in email automatically is decades old and was right for a long time. In the meantime two large providers have taken the problem on themselves — and in doing so have not only weakened the surveillance but largely destroyed the measurement it was about.
What an image proxy does
An image in a message is an address, not an image. When it is called, a connection is made from your device to the sender's server, and the sender learns everything any connection reveals: your IP address, the client in use, the time.
A proxy inserts itself in between. It is not your device that fetches the image but a server belonging to the provider. It fetches it, stores it, and serves it to you. The sender sees the provider's connection, not yours.
Google has done this for all images in Gmail since 2013. Apple has done something similar since 2021, but with one decisive difference.
The difference between the two
Gmail fetches an image when you open the message. So the sender still learns that and when it was opened — just not from where and with what. Because the image is cached afterwards, a second opening no longer counts.
Apple goes further. The protection fetches the images of all incoming messages in advance, regardless of whether you ever look at them. To the sender, every delivered message therefore looks like an opened one.
That is not a side effect but the point: a report that always arrives carries no information. The sender can no longer measure opening, because they measure it for everybody.
What this means for open rates
Open rates have not been a dependable figure since, for two opposing reasons at the same time:
- Inflated by pre-fetching: every recipient whose client fetches all images counts as an open. With an audience holding a high Apple share, that produces figures unrelated to attention.
- Deflated by caching and by recipients who do not load images at all. Those openings happen and are never reported.
Both distortions act at once, in an unknown ratio, and that ratio shifts with the composition of the list. A comparison of two campaigns to the same audience still says something. An absolute figure says nothing.
The gap that stays open
No proxy touches the links. Click something in a message and the connection goes straight from your device to the destination — or to a tracking address that notes the click. IP address, client, time: all back again.
That is the more practically important insight. Image protection works in the background and costs you nothing. The click is the act that actually discloses something, and the only defence against it is not making it.
Two further limitations worth knowing:
- Apple's protection belongs to the app, not the device. Use the Gmail app or another client on an iPhone and you do not have it.
- A proxy is a reader too. It knows which message contained which image and when it went to you. You are not trading observation for no observation, but many observers for one — one who has the message anyway.
For senders: what to rely on instead
The figures that still hold are the ones further down the funnel:
| Figure | Dependable? |
|---|---|
| Delivered (accepted, not refused) | yes — it comes from the receiving server, not the client |
| Opens | no, see above |
| Clicks | yes — with a discount for security filters that fetch links in advance |
| Unsubscribes and complaints | yes — and the only ones that affect deliverability directly |
| What happens on the page afterwards | yes — and the only thing that was ever the point |
There is an awkward side effect worth thinking through: anyone using opens as the marker for "active" in order to prune old addresses has been pruning wrongly since pre-fetching began. Recipients with Apple's protection count as permanently active even if they have read nothing for two years — and they are exactly the ones you want to identify when building deliverability.
And the tracking pixel itself? It has no business in an order confirmation or an invoice. It measures nothing anybody needs there, and it contributes to the impression that the message is a marketing campaign.