I've self-hosted my email on my own domain, own box, in my own home, on my own internet connection for two decades now. I've not had trouble being marked as sp

I've self-hosted my email on my own domain, own box, in my own home, on my own internet connection for two decades now. I've not had trouble being marked as spam, I have set up dkim and spf. The real reasons you cannot self host is a combination of: ISPs blocking outgoing TCP traffic with destination port 25 and does not provice a smart-host / relay for you to use or does provice a smart-host, but do not document it, or configures it in such a way that it only relays if you have some authentication that you don't, or that reverse-dns is configured (at the same time, they do not provide reverse-dns for you).