There are many claimants, and Google search reveals a lot of SEO'd information. I am genuinely curious about how the protocol evolved, and please include references based on your statements.
We had email on our IBM 370 back in 1978. It was implemented using a virtual card reader/punch device driver using the as-mentioned VNET.
https://en.wikipedia.org/wiki/History_of_email
(and it wasn't that one guy.)