You can get an email when there is a new post on your topic or reply. But you need to set that up when you post the New Topic or Reply.
Use the "New Topic" "New Reply" button or "Full Reply Screen" button to post. Using the Quick Reply box at the bottom of a topic page doesn't have the option choices you need.
* When you post your topic or reply, click the checkbox that says, "Add this thread to my watched topics"
* After submitting the post, click on "My Stuff" on the horizontal menu bar and choose "Watch Lists"
* On the Watch Lists page click on "Watched Topics"
* On the right click on "Edit Watched Topics"
* On the Edit page, on the right, click the "Immediately" button for Email Notification
* Click "Update"
You can go back later to remove the topic from being watched or chose No Email Notification if you want.