Safe solution to export Mac Mail

Can anyone help me to export Mac Mail accurately? I’m using Apple Mail, but I also want to access my email account data from other email programs also, because I need to access my account from different systems. Moreover, I want to expand email access in several platforms, if any time I need to access it from some other place, where I can’t access my system. Does anyone have an intelligent solution that is perfect to keep content safe while moving the data files?