By default an email notification will be sent to you if anyone replies in a topic that you have communicated in.
This is different than recieving
notifications of new topics.
To recieve replies in topics that you have not yet posted in you may do the following
-While in the thread select the 'Notify' tab at the top right of the topic. This will subscribe you to that topic. If you were already subscribed the system will notify you and ask if you would like the subscription cancelled.
See the attached screenshot
