By default it seems that when you create a post or reply to one, you are not subsribed to it. Which means if there are any addditional post, you will not be notified.
Instead, set it to always subscribe:
At the top Right of the Screen, click "Settings", Then on the left mid way down, click "General Settings"
Then look for the box labeled "Default Thread Subscription Mode"
Select "Instant Email"
Also, Categories are good and bad. Often categories cause posts to go unnoticed. To avoid missing something of interest or of value, view the forum not by the various categories, but using the "Active Topics" button at the top center of every page.