What Google, Yahoo, Microsoft, and Apple are doing to your email (opens in new tab)

Google, Yahoo, and Microsoft stopped being transport layers years ago. Apple did the same from one layer up, through Mail on iOS and macOS. The four have become active intermediaries between brands and their customers, mediating visibility, extraction, ranking, and interaction. They have spent the last decade publishing papers and patents about how this works. Most of it is open and citable.