Google will not be able to kill smtp, gmail is only one side of the email market. They’d have to offer a transactional and marketing email service and get every app/company to use that over smtp. It’s monumental and I don’t think it will change for decades.

You can damage open/federated email without having to break the lower level layers. See winmail.dat for instance[1].

I don't know if it's still in the pipeline but I remember that Google proposed an "AMP for email" not so long ago, with basically self-updating email contents.

Open email can be severely damaged if good old SMTP is only used to tunnel proprietary formats, especially if those formats are effectively just metadata that's used to fetch the actual content of the email from 3rd parties.

[1] https://en.wikipedia.org/wiki/Transport_Neutral_Encapsulatio...

They'd have to cooperate with Microsoft, which hosts email for a large number of companies.

Don't agree here.

Most companies use mail internally or to interact with customers usually using some type of external mailing service.....