[Kolab-devel] Preventing local users from being present in all domains

I'm running a multi-domain setup of kolab 3.1, in which I have 
discovered that
the default configuration, through its use of the 'mydestination' 
postfix
parameter, seems to put all local (UNIX) users on the server, as well as 
the
content of /etc/aliases into every domain. Users and aliases configured 
through
kolab take precedence, but if those do not exist, lookup falls through 
to local
users and/or /etc/aliases.

I would like to get rid of this behaviour, so as to not pollute my 
domain
namespace. Setting 'local_transport = error' in main.cf seems to make 
delivery
fail (but not with a very helpful message) on anything not in kolab 
LDAP.
However, I suspect this is not the right way to go about this. Ideally, 
I would
like /etc/aliases to work, so that I can populate it with global 
postmaster and
root accounts that would then work for every domain; but to prevent 
postfix from
looking in /etc/passwd for local users.

Is this possible? And if not, what is the proper way to get rid of the 
local
delivery?

Also, is the behaviour described above intentional for kolab? :)

Thanks in advance,

-Toke