I’m aware most ISPs do not allow for port 25 to be open for email use outside of business licenses, but at what level is that controlled? Can I get around that by owning my own router? Owning my own modem or ONT? Or is this just a thing they mystically control further up the pipeline that a relative layman such as myself can’t get around?
You can use a port reflector service. No ip.com might still offer it. Basically forwards anything incoming to their ip on port 25 to your ip and whatever port you specify.