New Post Notification Preference

New Post Notifications controls the way users and administrators receive email 
notifications of new posts to existing Topics/Requests.  You can control this 
feature at the Portal level by navigating to:

   My Account -> My Portals -> Edit

Under "New Post Notifications" drop-down menu there are three options which are 
as follows:

       A: Subscription Based (Default)
     B+A: Always Notify Admins When Users Post
     C+A: Always Notify All Users When an Admin Posts
   A+B+C: See All Of The Above

This is the Default and it's always enabled.  When users (including Admins) 
make at least one post to a Topic they are automatically subscribed to all 
future updates to this topic.  The system will automatically notify all 
subscribed users whenever a new post is made to the Topic.

In addition to Option A whenever a new post is made to an existing Topic all 
Administrators of this Category will receive email notifications.

In addition to Option A whenever a new post is made to an existing topic by the 
Category Administrator ALL Portal users will receive an email notification.  If 
a Topic belongs to a Category with "One-on-One Mode" set to "Yes" then only 
Administrators and Topic's owner receive this notification.

This is simply all of the above options enabled at once.

   Please refer to Portal Email Logs FAQ