If you're using Mastodon or email you need a server with a public IP address, which most people don't have. Distributed solutions like Secure Scuttlebutt (SSB)

If you're using Mastodon or email you need a server with a public IP address, which most people don't have. Distributed solutions like Secure Scuttlebutt (SSB) don't require that, so you can pass messages via any available relay server, LAN, or even a sneaker-net. It's also worth mentioning that most people have to trust their Mastodon / email provider not to snoop in their private messages. Systems like SSB provide true end-to-end encryption that makes it safe to broadcast your private messages to the world.