Hey there,

If you only system send notification email to your member instead of other member, you have to turn this `Notify all users on new post` setting off.

Also can you try download my attached files and replace into following files and see how it goes?
JoomlaFolder\administrator\components\com_easydiscuss\includes\mailer\mailer.php
JoomlaFolder\administrator\components\com_easydiscuss\includes\post\post.php

After you update the file in your site and the system didn't send correctly what you set the permission from category, can you provide us with your Joomla backend and FTP access so we can better have a check?

By the way, in the future you can just include your site's access once at http://stackideas.com/dashboard/site rather than needing to keep adding them in your replies