How can any modern article on spam not have a single reference to spf and dkim? There is nearly zero need to read the contents of an email message to determine

How can any modern article on spam not have a single reference to spf and dkim? There is nearly zero need to read the contents of an email message to determine 'spam' / 'not spam'. And if you read the PDF paper from 2006, you'll note this is exactly how it's done at Google. Google has its own internal reputation system, but it also relies on external services too. In short, a spammer can buy a clear shot to gmail inbox. E2E has nothing whatsoever to do with spam mail. The only thing E2E will do for spam, is generate mountains of encrypted spam.