I recently upgraded from 6.1.1 to 6.5.5

I have some complaints from users because of an apparent change in the email notification of replies to their posts.

I do have notification turned on as an option.

Seems people now have to go to the trouble of clicking the "favorites" box for every post or thread they make, or they will get no notification.

People want to just set something in their profile, and always thereafter get email notifications of all replies to them. As it was before.

How can I fix or change that ?