@luis_in_brief @silvermoon82@strangeobject.space @ben
I have, I can honestly say, been running mail servers on and off since some time in the mid-nineties. As I am today. It was never impossible.
What would make it hard would be the lack of static IP address, or access to rDNS. Anything that would prevent one from obtaining such is unequivocally a "big player" decision.