[turba] addressbook is shared with other users with same username [bug?]

[Alain]

Group, we're running horde/imp/turba on 1 server, and let
people choose the mailserver to connect to. When a user
'test' connect to server 'server1', and creates entry's in
the turba addressbook, another user with the same name
'test' that connects to server 'server2', get access to the
same turba addressbook. So i conclude that turba see the
username as something that is unique, but it isn't. Is there
a way to get turba to see username+server as something
unique and not online the username?

Maybe this is even a bug, since horde/imp has been made as a
multiuser & multiserver application.