Yes, it even happens to me...somebody hacked the email.

It happens to anyone, even a tech person.  I get a little email telling me that there have been strange activity in my email account.  (First step, do not log in from the link that was sent you.  Go to the address bar and go to your email web page and log in.)   So I log into my email account (hotmail in this case).  They have a neat feature under security that will tell you when you logged in and where in the world you were when you did.  So after seeing that "I" logged in in New York and Atlanta, I knew it was time to follow my own advice and use two factor authentication.  For you Yahoo accounts, it just means that if you log in on a new computer, you will have to enter a code sent to your mobile phone.  You can designate a trusted computer (the one you always use), if you or anyone tries to log on with any other device, you have to enter the code sent to your phone.  For GMail and hotmail, they allow you to use Google Authenticator, which provides a secure code on your phone that you have to enter if your account is attempted to be entered with a non-trusted computer.  Best way to secure your email account.  I wish I would have listened to myself earlier.