I'm not sure why you are being downvoted because this is a very legitimate question. Fortunately it's not hard to see that email, and Tomlinson's contributions, were incredibly novel and have shaped a lot of "good parts" of the internet today.
Although obviously email was conceptually based on a very old notion of communication, embodied, as you point out, by many media that came before it, it had to solve a few small, specific problems inherent in moving messages from one system to another via a simple network protocol.
The use of the "user@___domain" notion of identity seems mundane today, but in some important ways it was a huge breakthrough in the way that people thought about humans and the systems that need to work in order for them to be contacted.
Although obviously email was conceptually based on a very old notion of communication, embodied, as you point out, by many media that came before it, it had to solve a few small, specific problems inherent in moving messages from one system to another via a simple network protocol.
The use of the "user@___domain" notion of identity seems mundane today, but in some important ways it was a huge breakthrough in the way that people thought about humans and the systems that need to work in order for them to be contacted.