The post office system is socialist, so are functions like public roads, and fire and police services.

I’d argue that having the government provide a service isn’t enough to call something socialist. In “The Wealth of Nations”, Adam Smith said that in a free-market economy, the governments role was to provide defence, law and order, and public works (eg. roads and education). If we’re using Marx’s definitions for communism, then surely we have to use Smith’s definitions for Capitalism.