I was struggling to wrap my head around how federated social media works until I realized that email has basically been doing the same thing for 30 years. Different email servers are like instances of a federated network. You can send emails to people from within a single server or you can send emails to people on any other mail server. Your email address is a username followed by an ‘@’ and the server address, just like on Lemmy. Email is a decentralized service I’ve been using the whole time!
I use GPG mail with Apple Mail client and it works great. Just need to get the public keys of people you want to send encrypted email to.
Not sure how anyone can say “GPG” and “Works great” in the same sentence tbh. GPG is a usability nightmare except for the most advanced users who use it. Good luck trying to get your house contractor or doctor or representative or non-techie friends and family or really anyone to give you their “public key”