Here are some things that I’ve found out about email. I’d like to understand its history and then the state of the art.

It’s a federated system (I found this out from The unrealized potential of federation).

Other things I read around this time:

Message transfer agents transfer messages to each other using SMTP (RFC 5321).

The messages they transfer conform to the Internet Message Format (RFC 5322).

When reading about why Fastmail won’t incorporate PGP support:

It’s interesting how many things rely on putting data in DNS records.