John Postel created email. You can research ARPANET and RFC822 for the SMTP messaging standard.
He is notable for his widely discredited claim to be the "inventor of email",[4] based on the electronic mail software called "EMAIL" he wrote as a New Jersey high school student in the late 1970s.[5][6] Initial reports that repeated Ayyadurai's assertion—from organizations such as The Washington Post and the Smithsonian Institution—were followed by public retractions.[5][7] These corrections were triggered by objections from historians and ARPANET pioneers who pointed out that email was already actively used in the early 1970s
https://en.wikipedia.org/wiki/Shiva_Ayyadurai