Gregory's ServerSomething I know a little something about.
The forgoing post is only partly true.
Can you stand up an email server, open the ports, and hope to play nice? No, you can't, and it isn't because of evil gatekeepers, but because of the necessity of keeping spam traffic off the network.
I run email servers right now, and have off and on since the 1990s. My servers are hosted on private domains.
It is a straight pain in the ass, involving several layers of security, involved participation in a variety of DNS and SSL based security patterns which are somewhat effective today and may well not be effective at all tomorrow.
I'm playing by those rules, and will continue to do so as long as my emails continue to be delivered.
Anyone making this argument is either ignorant or simply doesn't want to deal with the trouble of running a modern email service.
Or maybe they're just being completely disingenuous; what I do know for certain is that my emails continue to be delivered.