Shared folders in kolab

Hi,

I ran in some problems accessing the kolab shared folders. First: I have
two hostnames and two domains configured in kolab-webadmin. One is the
local hostname (called "local"), the second one is my fqdn, accessible
from WWW (lets call it "domain.com").
I then created some test-folders in kolab-webadmin with all four
possible combinations (@local, @domain.com, located on both of them...)

But it seems that I only am able to access the folders from the local
hostname in IMAP with users, that were configured to have an
email-address that is user@local.

I dropped then the local name, named the kolab server domain.com. But I
am not able to access shared folders ([email protected], located on
domain.com, accessible from anyone). What's the problem here?

Any hints are appreciated.

regards,
Henning

PS: I can share folders via acl-plugin of roundcube. But that's not
"serverside", admin-controlled and neither beautiful if you know what I
mean...