New domains and new IPs are penalized heavily by most services' spam filters. My guess is that a lot of people try it, have poor delivery rates, and abandon th

New domains and new IPs are penalized heavily by most services' spam filters. My guess is that a lot of people try it, have poor delivery rates, and abandon the effort before they have enough time to develop decent domain & IP reputations. I've been running my own personal mail servers since 1995, on my current IP addresses since ~2016. If I add a new domain to my configuration, it takes 1-2 weeks before Gmail will reliably accept mail from it. Once I wait that out, delivery is mostly flawless.