What happens if your emails are logged on 2 different computers at the same time?

say you log onto your email on computer A but don't log off. So you log on to your email on computer B. What happens to your email that was logged on computer A?What happens if your emails are logged on 2 different computers at the same time?
Nothing email client will know its a different IP. You will have to sign in again.What happens if your emails are logged on 2 different computers at the same time?
nothing will happen. may be it take time to access