If everyone ran their own SMTP server, SMTP would still not be decentralized. There are additional points of failure on simple federation that are outside of th

If everyone ran their own SMTP server, SMTP would still not be decentralized. There are additional points of failure on simple federation that are outside of the owner-operator's control. Their domain name can be frozen or stolen by the registrar (this actually happened extensively to many websites, most notoriously The Daily Stormer which was suspended by dozens of "free speech" registrars and dozens of national ccTLDs). They can be denied IP transit or transport, or blackholed by specific ASNs. Decentralized protocols will provide graph access in absence of centralized resources.