There are a million wrong ways to self-host email, which are usually default, and there's a lack of standardization between all the different servers and client

There are a million wrong ways to self-host email, which are usually default, and there's a lack of standardization between all the different servers and clients. Like, it shouldn't even be possible to accidentally send unsigned email, and every server should totally reject it (Gmail still accepts it!). Any old or insecure modes should've all been banned, kinda like how web browsers force min versions of TLS and heavily discourage plain HTTP. I don't have a lot of experience self-hosting email because of how quickly I lost patience with it. Had more experience with XMPP, which had similar problems. If you're going to make a federated protocol, it has to be strict, otherwise a big player will lay down the law instead.