My HTC M9 won't let me access my emails from wifi

[AC Question]

When the phone tries to update the emails it tells me login failed, I go to settings, which are already filled in, and press next but it checks account settings and tells me some of the information is incorrect and to review and try again. I don't know what is entered incorrectly. I have checked it has the correct email address and password (the same as my yahoo account) but I don't know how to check the other things it needs. Please can someone help?