I want to create a special Group Directory structure for my Users.

/home/groupA <-- home folder for groupA where every user of groupA can create/edit/delete files

/home/groupA/Public <-- Public Folder where every user can read files

/home/groupA/Public/Dropbox <-- Folder where every user can write files but only users of groupA can access this directory and create/edit/delete files

Now I have:
4 drwxrwx--t 10 nobody groupA 4096 Feb 18 15:44 /home/groupA
4 drwxrwxr-x 7 nobody groupA 4096 Feb 18 15:40 /home/groupA/Public/
4 drwxrwx-w- 10 nobody groupA 4096 Feb 18 15:55 /home/groupA/Public/Dropbox

My smc.confcontains the following entrys

[groupA]
path = /home/groupA
comment = Folder for users of groupA
browseable = yes
read only = no
create mask = 0770
directory mask = 0770
force group = groupA

[groupA Public]
path = /home/groupA/Public
comment = Admins Public
Browseable = yes
write list = @groupA
create mask = 0775
directory mask = 0775

[groupA DropBox]
path = /home/groupA/Public/Dropbox
comment = groupA Dropbox
read only = no
valid users = @groupA
browseable = yes
inherit owner = yes
directory mode = 3770
force directory mode = 3770

The working part is: Users of groupA can access and fully use /home/groupA
All Users can access /home/groupA/Public/ and read the files from there.

My problem is that all users, even those who are not in groupA can access the /home/groupA/Public/Dropbox and see all files. I just want them to be able to put files in there but not see the content of the folder and prohibit them from deleting any files in there.

Does anybody have a clue what could be the problem and how I can fix it ?