Why bother killing anyone? We're only talking about email here. The tech oligopoly can do whatever they want here, and no one can do anything about it. Well, they could, technically, but they're not going to: we've seen over and over that users will always choose the most convenient choice, not the one in their best long-term interests. We've also seen that governments will do little to nothing to counteract this oligopoly when it abuses its power or becomes monopolistic.