How to hide some folders using Kolab server

Hi, this is my first post in this list.

I use Kolab server that is a groupware with Cyrus, so the users have special folders for storing contacts, tasks, and calendar in XML format.

Because of it, using RoundCube I see these IMAP folders that should be hiden. Is there any way to hide them? Of course I cannot unsuscribe from them, I need to be suscribed for use them in Kontact.

I've read the entiry main configuration but only found the following:

// only list folders within this path $rcmail_config['imap_root'] = '';

But I don't know how to use it, and in fact I don't know if this the solution to my problem. May be?

Thanks for any help.