Email failure: "Error: Login to the account failed, please try again."

[NGOLDEN]

sbcglobal.net - won't auto add, won't allow manual add, wireless is off, have deleted email AND Yahoo mail accounts, but can't re-add, turned phone off and on. Was working until yesterday, then stopped downloading mail.  Amusing correct username and password and have no problem accessing web mail from PC. Have not dropped or damaged the phone.  Feeling hosed here. Any ideas how to make it work again?