Disappearing emails through yahoo and cell phone if AOutlook on main computer at home is open.

It took be forever buy my home email is now working with uverse incoming and outgoing with outlook.  Now I can log in to my account with yahoo from another computer but I can't see any emails if outlook is open on the home computer.  It does this on my phone as well.  If my outlook is closed then there isn't a problem.  As soon as outlook is opened the emails disappear and do not appear again if outlook is closed.