I understand that you want to update your students on certain topics, but please don't force-subscribe us to all of the forums. It clogs our inboxes with repetitive replies and answers by fellow classmates.
If you do want to update us on new topics, do so only when you start a forum, or when it is you who is posting. Provide us with the option to unsubscribe from the forums, because as far as my patience has gone, all of the emails I get are one and the same from different people at different times.
tl;dr: Turn on the unsubscribe option.