[jhugo]

> Well that's the thing, if they were self-hosting or using smaller providers, they probably wouldn't all have the new features.

They are really not difficult to implement. Like, 10% extra effort on top of deploying a mail server gets you all the modern security features. They are really not relevant in the question of whether someone self-hosts or not.

> And I'm surprised emails from your server aren't being filtered out as spam going into Gmail inboxes.

Implementing modern SMTP security features helps with that, and keeping the same server for a long time. In the first year or two my mail used to occasionally get sent to spam (but that was also before several of the modern security features existed), but once your IP has been sending mail for two decades and has never sent a single spam message, you tend not to have a problem with reputation.

> An open protocol success story is HTTPS. Nearly everyone is forced onto fully-compliant new versions, and self-hosting is more viable than ever.

Notably, the decentralisation mechanism for HTTPS and SMTP is identical, and the transport security mechanism is identical. The effort to self-host mail is higher, but that would be completely solved by a modern 'plug & play' mail server implementation. Once again, the protocol is not the issue here at all.