> I finally gave up and switched entirely over to Fastmail awhile back. No more delivery problems, but no more self-hosting my own e-mail, something I'd done for twenty years prior (my domain is older than Mozilla and Google).

Can anyone speak to what a provider like Fastmail does behind the scenes that guarantees their delivery? Is it the threat to sue/kick up dirt/raise issues with the appropriate regulatory body if perfectly good emails don't go through? Merely having a seat at some sort of regulatory body or committee?