Kolab Webadmin not working (anymore)

Hi knowledgeable folks,

as of recent I cannot create new users with the kolab-webadmin. I tried 
restarting the services, the server, updating and praying. Nothing 
helped thus far.

The problem seems to be the lack of the preselected E-Mail server on the 
4th tab of the new user dialog. For existing users there the field is 
filled with localhost.

I did not change any configs or did otherwise tamper with the server.

How can I get kolab-webadmin talking to the rest of the system again?

With kind regards

Torben Mohrfeldt