> Nobody's talking about the world moving away from google. We're talking about the world simply not having non-repudiation built into email. A sender of an email doesn't owe you non-repudiation as a feature. Sorry if you think otherwise. Senders can add non-repudiation as a feature if they want to, which satisfies your purchase receipt scenario.
Please explain to me how I can make Amazon (or any other webshop) add non-repudiable contracts to their order flow? That's right, I can't. And no, I don't think that Amazon "owes" me non-repudiable emails, but now that we have non-repudiation by accident, it's certainly nice to have, and the world would be worse off if we removed that feature and replaced it with nothing.
You can't force their DKIM signatures to be good forever either. You're basing some sense of security on a cryptographic property that simply isn't true. Would the world be worse off if you couldn't rely on DKIM signatures indefinitely? I don't know, are we worse off? Because whether you accept it or not, that's the exact situation we're in now.
So if something does not provide a perfect guarantee, it's "nothing"? You realize that handwritten signatures on a paper contract do not provide a perfect guarantee either? Signatures can be forged. And the paper is not going to remain in perfect condition forever, at some point in the future the paper is going to decay. Does that mean we can never know anything about anything? No. Of course we can have evidence about events which occurred in the world, even if the evidence doesn't provide a 100% guarantee of something, indefinitely. For example, a handwritten signature on a paper can be imperfect evidence that the contract took place, or a DKIM signature on an email can be imperfect evidence that the email is not a forgery.
Please explain to me how I can make Amazon (or any other webshop) add non-repudiable contracts to their order flow? That's right, I can't. And no, I don't think that Amazon "owes" me non-repudiable emails, but now that we have non-repudiation by accident, it's certainly nice to have, and the world would be worse off if we removed that feature and replaced it with nothing.