If you participate in, or just read a particular thread, or are watching a particular member's trades, you can be sent an instant email when a new post is made.

Simply go to your UserCP and in the left menu click on Edit Options. Scroll down to the box that says Messaging & Notification, and go to...



You can select the option you wish, but selecting "Instant email notification" will keep you updated on new posts.

If you have posted in that thread, you will get the notifications. If you have not you will need to subscribe to that thread. You can do that in the drop down menu called "Thread Tools".