If you use GMail, AI (Gemini) was turned on yesterday by default and now scans all of your content for machine learning. To turn off, go to Settings>General and scroll down. Uncheck the box for "Smart features."
There's other "Smart" add-ons as well, but that's the one that reads your content.
*sigh* I have been moving the email show from outlook to proton because of how invasive copilot was. I can't say for shure proton is any better though.