I would suggest you to rest the password immediately . You can easily go to att.com and select "forgot password". please don't worry all AT&Ts are more safe and Secure and your email will locked for security purpose if someone trying to access your email.
In case if you're still unable to reset the password. You can contact AT&T to reset the password, please call:877-267-2988.
I would recommend you to change the security question and password once you done with password reset.