> E-mail was an absolute disaster because there was no barrier to entry for someone who just wants to send unsolicited garbage to everyone. Email spam is possi

> E-mail was an absolute disaster because there was no barrier to entry for someone who just wants to send unsolicited garbage to everyone. Email spam is possible because of the expectation that you can contact someone you've had no prior interaction with. (Also, it at least used to be quite easy to spoof the sender address because participants couldn't cryptographically prove their identities, but we now rely on tech like DKIM to mitigate this). Messaging apps have an easier job because the services can refuse to deliver messages to people who haven't already received your public key (or some short, per-contact, pre-shared secret). In fact, email encryption could also work this way, if users first had to send a standardised introduction message, and servers rejected any further messages until the recipient had marked the sender as trusted.