Hi Bundaleer
Whenever you create or post in a thread you get 'subscribed'. This means you receive email updates.
When you create your message, there is a check box at the bottom of the screen
"Check this box to have yourself notified about replies to this topic"
That box is checked by default so, you need to clear it.
You can manage your current subscriptions by clicking on My Profile then My Subscriptions. From here you can delete all the subscriptions you have previously made.
This is how it should work, if that isn't working for you please let me know so I can investigate this as a bug/fault.
Hope that helps!
Rob