E-mail notification

Hello. This one is really for the TR people.

Each time I participate in a discussion or contribute to a question, I click the little checkbox at the bottom of the page which says “Notify me by e-mail when new posts are added to this thread”.

However, I have never once received such an email notifying me of new posts to the thread. I have checked that my account holds the correct email address, I have checked my spam folders. This feature as far as I am concerned simply does not work.

Can anyone shed any light on this problem?
Thanks
Ed