If you follow specific forums you will get emails when someone posts in the forum. Or if you tick "Email me when someone replies" when you post or reply, you will get emails when someone replies to your post.
There are two things you can do.
1. Unfollow the forums. If you don't want to receive notifications about a forum, make sure you are not following. Check for an "Unfollow" button and click it to unfollow. You should stop receiving emails for that forum.
2. Change your notification settings. Click your profile icon at the top of the page, select "Account Settings" then "Notifications". There are quite a few settings you can change to tweak things.
Note: The email function is a bit broken, so I can't guarantee this will fix your problem but it should help.