Earlier quoted context omitted.
This is really the only way to reject AMP4Email: Refuse to allow it, so that companies wanting to reach their customers can't implement it. However, it's unlikely large mail providers would choose to do this, I can't imagine Microsoft or Yahoo taking such a stand. My own provider FastMail, has said they of course, can't promise they won't support AMP4Email since compatibility is a major goal of theirs, and I can't fa…
If you run Amavis you can add a MIME type to the $banned_filename_re in a conf file (on debian based derivatives you'll normally find that in /etc/amavis/conf.d/20-debian_defaults). qr'^application/amp+html$'i, is what I use. If you want to put it in a separate file (such as a local config file) then you can just push(@$banned_filename_re,qr'^application/amp+html$'i);
qr'^application/amp\+html$'i,