https://github.com/davepinch/pinchy.cc/blob/master/content/topics/computing/history-of-email/history-of-email.md
Because of interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet, or soft (low-energy) X-ray wavelengths.
History of email (Wikipedia) The history of email entails an evolving set of technologies and standards that culminated in the email systems in use today.