I'm guessing they are thread updates. The reason this happens is because when you sign up for the forums, your settings are pre set to automatically subscribe to topics. So here's what you need to do.
Click on "Settings" in the top right of any page of the forums. Then, in the left hand column you will see "General Settings". Under "Messages & Notifications" you will see "Default Thread Subscription Mode". Click on the drop down menu and choose "Do not subscribe". Then scroll down to the bottom and click "Save Changes".
After you have done this it will stop automatically subscribing to every topic you post in, but you are still subscribed to the topics you had posted in before you made these changes so there is one more step to stop getting these emails.
Click on "Settings" again, and at the top you will see a list of subscriptions with new posts. Next click on "View All Subscriptions". This will show you all the threads you are subscribed to already. Click and put a check mark in the box to the right of the list above them all. The right box is circled in the picture below. After this you need to click on "Selected Threads" to drop the menu down. In the menu select "Delete Subscriptions" and then click on "Go". These are all illustrated in the image below.
You most likely have a few pages of subscriptions so you will need to keep doing that second part until all the subscriptions are deleted.
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