It's very easy.
1. At the top center of your screen you'll see
MY STUFF, click on it.
2. Then click on
EDIT PREFERENCES.
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3. Then scroll down about 3/4 of the way to the bottom until you see
By default should anything added to your Watch Lists be emailed to you? Click on
YES.
4. Just below that is
Do you want to be notified via email when you receive a private message? Again, click on
YES.
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5. At the very bottom of the page click on the
SUBMIT button.
6. Whenever you begin your own topic you will be notified when someone replies.
BUT, if you are replying to another members topic you will need to check the
Add this thread to my Watched Topics box if you want email alerts from that topic.
NOTE: The picture below is found when you reply to a topic. It is not in your Edit Preferences section.