The history of email entails an evolving set of technologies and standards that culminated in the email systems in use today.
[C. P. E.] Bach, armed with a recommendation by the Graun brothers (Johann Gottlieb and Carl Heinrich) and Sylvius Leopold Weiss, obtained an appointment at Berlin in the service of Crown Prince Frederick of Prussia, the future Frederick the Great.
SNDMSG (Wikipedia) SNDMSG was an early electronic mail program, chiefly notable because it was used to send what is considered the first networked email.