If I’ve used someone’s iPhone to access my email and not signed out, does my account stay open to them even though I’ve later signed in and out on my home PC?

I accessed my email from a friend's iPhone but forgot to sign out.  does this keep my email open on his phone and accessible to him if he doesn't sign it out.  I've signed on and out on my home PC, but at times my email account seems to be already open as emails have been opened before I have seen them.

How do I shut off this other access to my email account??