Learn2settings
Similar to how you change your themes.
Click Profile
Hover over Modify Profile
Click Notifications
Uncheck the box next to "Turn notification on when you post or reply to a topic."
Click Save settings
And that's it. While you're there, you'll probably have a lot of "Current Topic Notifications" and maybe some "Current Board Notifications." If you no longer want to receive notifications for those, check the box next to any (or all) that you want to change and click Unnotify. You can check the top box in order to check all displayed boxes at once to saving some clicking.