Email, in some iteration or another (starting with RFC524), not only predates the internet, but predates TCP. The only older standardised communications systems

Email, in some iteration or another (starting with RFC524), not only predates the internet, but predates TCP. The only older standardised communications systems still in widespread use are the telephone and the postal systems. It's an unfortunate quirk of how the internet has developed that email has stuck around, like postal mail, as long as you put the correct address on the outside of the envelope, you can put almost anything inside. RFC 822 makes it clear this is a feature: > In this context, messages are viewed as having an envelope and contents. The envelope contains whatever information is needed to accomplish transmission and delivery. The contents compose the object to be delivered to the recipient. This standard applies only to the format and some of the semantics of message contents. It contains no specification of the information in the envelope.