Hi to all,
For each user with email account I solved this issue by modifying "sogo.conf.mas" file, here: /usr/share/zentyal/stubs/openchange/sogo.conf.mas
In section "/* LDAP authentication */" you must change "YES" to "NO" here: id = sambaShared; -> isAddressBook = NO; and here: id = sambaContacts; -> isAddressBook = NO;
In this mode, in webmail, nobody can see shared addressbook and shared contacts, even in the same domain.
I don't know if this is the answer what you espect.
Gabriel