@up201705417 a great write up on the unholy clusterfudge that is online communication in 2019, with some good historical background that I remember living through. @librelounge did an episode on this too:
https://librelounge.org/episodes/episode-18-the-rise-and-fall-of-instant-messengers.html
@goncalo it's getting even more complicated now that a lot of people are pushing encryption as a minimum standard and advising people to use Signal or Telegram (or even WhatsApp) instead of email or SMS. This is the consequence of decades of not making E2E encryption a basic feature of federated systems. Geeks actually pushing noobs to move from open comms networks to data silos (*shudder*).