The email messages are coming to you because you are currently "subscribed" to the discussion forum. This is an option that each course participant can control in forums that have optional subscription activated.
This is a two step process.
- First, in the top right corner of the course main page, find your name and click on it. Next, choose the "Edit profile" tab. Look at your individual profile to make sure your "Forum auto-subscribe" setting is set to "No ...".
- Next, go to the forum from which you are receiving the email messages. In the top right corner of the forum, at the same place where you would see the list of posts made to the forum, look in the top right corner to find the "Unsubscribe from this forum" link. Click to unsubscribe. Note that this is a toggle, so you can re-subscribe at any time by clicking on the same link to "Subscribe to this forum".
Thanks to Joan Van Duzer for the write up!