Hi Ray,
Yes, users can subsrcibe to email at the forum level, on the page that contains the forum it has a link for "Edit Notifications" and it has indicators next to each forum whether you are subscribed. For example on this site the forum page http://www.mojoportal.com/forums.aspx has these links. I am subscribed to allforums so I got notification of your post.
Note that it does require that you have valid smtp settings.
Hope it helps,
Joe