There are different settings you can check in your profile, from the online courses page, you click on your name at the top right, edit profile, and choose preferences. There you'll see a option for "forum preferences" which you can change so that you DO or do NOT receive posts.

The default settings for receiving posts from other people in your course is such that you are "subscribed" to each Forum automatically only AFTER you have posted in the Forum. So if you would like to receive all posts as soon as anyone posts, you will need to "Subscribe to all forums" manually as described below.

To change your preferences in the course page: on the left column there is a link to "Forums" under the participants block, click on "Forums", then on the forum page at the top right you will see two options – "subscribe to all forms" and "unsubscribed from all forms". If your course is missing the "Forums" link, then click on any of the discussion forums, then you can click on search forums, then on the top you'll see a link for forums.

Another tip for organizing your emails from the course posts is to set up a filter in your mail program so that all posts are put into a folder and not your inbox, then if you ever want to you could go back to them in one place.