How do you log out of your AOL account on your I-pad mini?

How do you log out of any mail program on an Android tablet? the concept of "logging out" just does not seem to exist - making this a massive security issue. It's mind-boggling that Android apps like email, and other ones that can contain personal messages and data, have no "log out" or "shut down" facility. It just shows that these expensive smart tablets are really only fashion toys, geared essentially to music and games, and that the big companies like google who are behind them really have not designed them for serious users, whatever they claim