response arrow in apple mail email does not work

The conversation has been ongoing for a year... the response arrow left of an email does not open up the response if clicked. It opens the same email in a new window. Prior OS versions opened the response so I do not have to go searching for it or have the entire thread view. Apple Support told me my host site controls that arrow.... I do not believe them since there are so many other users with the problem. My host is BlueHost. Any ideas???