Popular iOS and Mac email apps scrape inboxes to profit from personal data, report finds [U]
I think that people sometimes forget: this is practically the definition of a modern mail client, lol. Hell, some actual mail services describe this sort of thing as a feature, if you really want to be pedantic.
In fact, it’s part of why I was very hesitant about switching to Gmail many years ago. Because it would place my mail under the privacy policy of an advertising company, and probably one of the most likely ones to unleash SkyNet upon the world in some distant future.
With modern mail clients, now you often need to decide whether or not you trust the company that made your client, not just the folks running your mail servers.