I could fix the join MUC problem if not assigned by changing the configuration to member-only like I said. Seems to work.
Edit: I was trying out some more and I still got a problem. When making
By changing default MUC configuration I could prevent other users for creating MUCs, but when I do a GroupBookmark and I do members only, noone of the members can join a room, because group bookmarks doesn't register users to a room.
The only thing now I need to fix is that user can message others...I'll go deeper in the XEP t hing now I guess. But feel free to give me some tips if anyone know something about it.
Best Regards.