I'm shouting into the wind here a fair amount, but I just discovered DeltaChat and ArcaneChat. ArcaneChat is available only on Android, but DeltaChat is available on iOS and uses chatmail relays. My family has found it to be super useful and effective. I don't think it's viable to convert everybody in my social circle, but I've been very happy with the apps and attachments, notifications, and general performance.
DeltaChat was much more useful when it worked with any email server and didn't need its own special kind of server. We have plenty of messengers that use their own servers, like matrix, XMPP, and simplex.
I appreciate the simplicity of hosting ChatMail versus a regular mail server. It's simpler, lighter weight, and better suited for the chat use case. It's basically the ideal messaging platform for my needs.
I've used both. Neither are as good. Your reply also completely ignores my point about the ease of hosting the infrastructure yourself. Prosody isn't too bad, but hosting Matrix is a nightmare -- as much as I admire what the Matrix crew is trying to do, the architecture is unwieldy and always has been.
"Usually, it just works, but for some providers, you need to adjust the settings. In this case, click on “prepare” for details.
Please note that push notifications do not work with classic providers and esp. large classic providers often have sending limits and overzealous spam rejections. This can worsen the chat experience, as messages are delayed or missing messages may even disrupt groups."
https://chatmail.at/
I'm considering running my own chatmail relay, although I haven't tried that yet.
That was their one big plus and while I avoided it because of PGP, this means that it really has no upside over XMPP for me.
Quote from https://providers.delta.chat:
"Usually, it just works, but for some providers, you need to adjust the settings. In this case, click on “prepare” for details.
Please note that push notifications do not work with classic providers and esp. large classic providers often have sending limits and overzealous spam rejections. This can worsen the chat experience, as messages are delayed or missing messages may even disrupt groups."