Doesn't Gmail and Outlook already anonymize tracking pixels? When I heard that announcement what I heard was, "we implemented a feature that Gmail and Outlook have had for years!". I don't think it will change the landscape all that much.
A lot of people assumed this is what Gmail did, but it wasn’t actually the case.
[1] https://twitter.com/rjonesy/status/1401993816001978375/photo...
(And no, I don't trust Apple not to associate this data with a user's Apple ID and datamine it in the future - if your country has lax privacy laws Apple will exploit it till the law says otherwise.)
Edit:
Here's another perspective - now, even if I don't use Apple's iCloud backup or email services, Apple has found another clever way to learn about some of the marketing emails I receive. That information is very valuable.
Given the wretched state of privacy laws in the U.S. that seems an uncharitable position. Apple has far more business motivation to treat its customers well in that regard than to try to squeeze money out of their data.
Although you’d think they’d have motivation to treat developers better than demanding a 30% cut, so there’s that.
However, I'd like to see the Privacy Policy (if it's available and in plain English) for this feature before concluding that they're not immediately discarding this data (or even just where I get my mail from, which is also very useful information to further lock me in.)
Compare this with Apple Mail which proxies emails from a different, presumably non-Google IP address and which does so only when an email is downloaded in the background. So while you can't track IP address, yes, and you never could set cookies that I'm aware of without clicking a link first, this means you can still track "downloads" of your email to a local client, just not "opens" - and if your Mail app already downloaded images when the email was downloaded, then it's possible it won't even change that - you might not have been tracking opens this whole time... maybe.
I searched around and found some articles that makes the same claim[1], but in my own testing that doesn't seem to be the case (ie. I had to click on the email before image would start loading).
[1] https://sendloop.com/articles/the-effect-of-gmail-image-prox...
Mozilla/5.0 (Windows NT 5.1; rv:11.0) Gecko Firefox/11.0 (via ggpht.com GoogleImageProxy)
When Gmail first introduced this image proxy feature in 2013 it started showing images in emails by default, which is great. I researched blog posts from then and apparently a workaround that still worked was to serve a fake HTTP Content-Length header of "0" and Gmail's proxies wouldn't cache the image. It's unclear if this bug has been fixed or not, or if similar bugs affect Outlook's proxies, for example.
The rest of this post is speculation -
I wonder if it won't affect Apple's Mail app because Apple isn't loading images directly from a proxy, instead, the original URL is sent to the Mail app over IMAP or Exchange and then Apple will download the image by asking the Apple proxy for the unmodified URL. This means even if an existing Gmail or Outlook image proxy server can be tricked, it shouldn't affect the Apple Mail app.
That's not to say Apple Mail won't have other issues - for example, it shouldn't stop at images. Apple Mail supports CSS and web fonts, so theoretically all network traffic not destined to hit the IMAP server should go through the proxy if complete privacy is desired. I think the wording of the Mail app suggests it's more than just images.
And the way it's implemented, because it's not server-side, it does indicate that an email address checked using Apple Mail downloaded your email, so you know it's pretty likely there's a human at the other end and they use Apple Mail even if they don't know exactly when you opened the email for the first time, they know when your Mail app downloaded it and possibly when you received a push notification about it. Unless it caches content with every request, which it might, you might also know how many different Apple Mail clients downloaded the message and when which might still indicate patterns of use especially if you can create a network of tracking pixels across different email messages. Finally, nothing about the feature actually anonymizes links or prevents specifically tracking pixels, but that's probably a good thing until we invent local Content Blocker extensions for Mail app, for example.