Concentration of email providers and clients means most users are not touching the "federated" part, and the federation continue to shrink.
@soller
I want to believe this good story. I've also barely convinced anyone with it.
I have tried to set up personal mail servers. Setting up a mail server had been quite technically challenging until recent years, requiring installing multiple components and tweaking configurations. After the technical hurdle, a new mail server has to overcome being considered spam by many existing servers. Then it has to overcome being spammed.
A plurality of businesses just throw the problem to Google and Microsoft. The trend is growing too.
“While self-hosted domains switched to providers across all categories, more than a quarter of them changed their mail provider to Google and Microsoft,”
https://today.ucsd.edu/story/IMC2021_savage
The client side is worse. From, ironically, a spam sender's data, webmail is 99% Gmail, Yahoo, Outlook; mobile is 95% iOS and Android default.
https://www.litmus.com/blog/email-client-market-share-february-2022/
In the end, "Nobody Wants to Run Their Own Server".
https://notes.alexkehayias.com/nobody-wants-to-run-their-own-server/