Lets face it, 90% of email goes through a few providers like Microsoft, google, and yahoo. They already have access to what we read, write, and comment on. They already have sophisticated tools to block unwanted content in spam and such, and sophisticated AI to analyze email for content.

I could see them banning alternatives like protinmail for "hate speech", blocking email accounts that don't meet "community standards", and also blocking certain words in email. They have even already developed the technology for China, which does it already. It doesn't seem like it's that far of a reach.