The government can subpoena your own server in your own house just as easily as they can subpoena Google's servers.

So who are you hiding from? If it's the government, then you must use strong cryptography no matter where you host your email, and you must ensure that everyone you communicate with is as paranoid as you. (I would encrypt all my email, but nobody else I talk too will. So it doesn't work.) If it's advertisers you want to avoid, just run your own server and stop worrying so much. People have been doing it for years.

(Although, I run my own mailserver and am inundated with spam. Thousands of messages a day. So you aren't really avoiding advertisements, you are just avoiding advertisements for stuff you might actually want :)