This is the problem with matrix et al. They have to offer something that is leagues ahead of the current baseline, which I'm not convinced they are.
I've been running my own email server for going on 20 years now.
[edit] To add to the above, I use the same Matrix server to chat in various Matrix, IRC and Gitter rooms, and also to host a couple of self-written bots which I use to control a few aspects of my life. Email isn't really a replacement for the things I use Matrix for.
Verify this, is this you that.
I think partly its because i am not always on latest version of Synapse so the self-updating clients expect slightly different backends but uff.
It feels like Moxie is right with his anti federation argument. Call me stupid but i am really trying to keep it together but i still cant tell why some of the popups show up or why some sessions of my friends wont decrypt and they show gibberish.
I set up my own server using Synapse, and invited about half a dozen other IRL techie friends to join me in there to continue chatting during Covid times.
Considering we've all worked in tech for decades and run our own servers/services, none of us can really work out how the hell it's supposed to work. I mean, after lots of time consuming verifying of devices it kind of works. Except recently, all of a sudden, one of the people in our main chat room can not see the messages I sent from one of my devices. It tells him to get my keys from another session, he has only every used a single device/session. There is no UI that either of us can find to help fix it. We can chat fine in a different encrypted room, or if I use a different device.
I'm not pulling anyone else into the Matrix ecosystem until encryption stops being just so god damn awful.