Calendar and contacts not showing up in Kontact

[Johannes Ranke]

Hi,

I am migrating an existing kolab installation to a different virtual server and 
have done a fresh install of Kolab 16 on Debian jessie.

Setting it up worked fine and I have created a regular Kolab user. The command

  kolab lm

lists all the folders I could dream of, including Calendar at domain.org and 
Contacts at domain.org.

However, I can not get kontact on the client side to use calendar and contact 
from the new server.

When I configure a kolab groupware account for the new server, I only see the 
email folders (Inbox, Archives, ...). Korganizer and kaddressbook have no 
entries for the new account.

I have tried with kontact 4.14.1 from Debian jessie, kontact 5.x from Ubuntu 
16.10 and current kontact from KDE neon, so the problem appears to be on the 
server side.

Any hints?

Johannes

P.S.: Maybe it is relevant that in addition to the new server 
kolab.domain.org, my old kolab 3.4 installation is still running on 
{www,smtp,imap,mail}.domain.org. Is it possible that this old installation 
gets in the way, i.e. kontact tries to talk that old installation, although I 
specify the new server kolab.domain.org?