You can very easily control the emails and/or notifications you receive about categories and topics on the forum.
Look for the "bell" icon -- It's in the upper right above each category. There, you can control the notifications that you receive for the category:
You can also choose to "watch" or "track" individual topics. Go to an topic, and start to scroll down. On the right you'll see the "bell" icon. Also, if you scroll all the way to the bottom of the thread, you'll see a larger bell icon with your notification selection:
How (and how frequently) you receive notifications and/or emails can be controlled from your profile.