Hi Isabelle,
You will have to approve all new forum posts programatically to make such a scenario work.
Here is a brief look at instructions:
1. At first, you will have to create a global event handler for new forum posts. More information about it is in
Developer's Guide - Global events.
2. For each new post (
ForumPostInfo object) which you can get using
CMS.Forums.ForumPostInfoProvider.GetForumPostInfo(Int32 forumPostId), you can call its
Approve() method which will ensure that it gets automatically approved.
A complete list of all API methods can be found in
API Reference.
Best regards,
Filip Ligac