When a Forum is created (or if one has been already created, just click on the Forum - Update).  Where it asks, “Force everyone to be subscribed?” select “No.”

To view a list of the Forums and your “subscribed status” for each forum:
In the Activities Block, click on Forums, and you will see a list of the forums that have been created within the course. To the right side of each, you will see your subscription status under Subscribed: “Yes” or “No.”  If you would like to change your status from Yes to No (or No to Yes), just click the button. 

*If you would like to change all of your subscriptions to "No" at once, just click the link in the upper right-hand corner "Unsubscribe from all forums."

Every time you "reply" to a Forum discussion, you may select, "I do not want email copies of posts to this forum."  Choose that option before you click the button "Post to forum."