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?
Microsoft’s Exchange Online Plan 1 is email-only and is 4/month per user. There are probably cheaper IMAP providers, but EO1 is full exchange: mail, global address book, calendars, etc.