Great detailed article by #[0] on the history of email.
That being said, I have to disagree with the final assessment that you can't reasonably host your own email. I've been hosting my own email for the last 20 years, most of which has been done at my own home, without a problem.
I highly recommend that if you value privacy, you consider giving it a try. I never have any issues receiving emails, my spam filtering is tailored to my own emails, my mailbox is clean from spam, I rarely have any issues sending emails outbound, and the best part is that I don't have anyone spying on the emails in my inbox.