This largely true and hugely disappointing. Our startup (https://portal.cloud https://portal.cloud) is making it possible for non-hackers to self-host their own

This largely true and hugely disappointing. Our startup (https://portal.cloud https://portal.cloud) is making it possible for non-hackers to self-host their own email servers. It works very well for the most part, but we have had to explain to a number of them why their email sometimes gets bounced by the big proprietary cloud services. All of our users have their own domain names, IP addresses, SPF records, and correctly configured (and up to date) Postfix SMTP servers. There is absolutely no excuse for not always delivering their email, and yet this is what the big companies do.