This is not able to exist anymore. While the server software itself can be automated, the never ending maintenance and defense of your IP(s) on RBLs, as well as the never ending cat & mouse game of spam fighting, is a full time job that only grows the more you use your email server.
If you use IPv6 this problem goes away, right?
>"as well as the never ending cat & mouse game of spam fighting"
This can be automated in a number of different ways.
The low-tech solution is to use consensus amongst users. Allow home servers to share spam lists, and if multiple users mark an email as spam it's marked as spam for everyone. You'd still allow individual users to whitelist email domains they didn't personally want marked as spam. Similar arrangements work well for ad-block lists, I see no reason why the same approach can't be taken for spam email lists too.
The high-tech solution is to use machine learning to pick up on clues that an email should be marked as spam. This wouldn't be something that individual users would need to manage, it could come built-in with the home email server software. It could also evolve over time, both from its own research and from human guidance.
Yes you can, you can run your own servers. Home servers don't have to be complicated to run, nor do they have to provide every online service ever conceived. An easy to run email server could be something that proves popular.