Sounds like you know enough about this process where you know it can be a lot of setup and careful maintenance.

So if you don't want to invest the setup and ongoing maintenance time, or get no pleasure from doing such , may I ask why you want a simple way to do all this at all?

Seems like you should just use fastmail or gmail or similar?

Configuring and running smtp isn't supposed to be super easy and fool proof. I think most systems that claim that will leave you with an unmaintained email solution that is likely not very secure and probably not being replicated or backed up, for starters, not mentioning all the actual things that go into making it all work reliably.