@morrow without logs this will be hard to track down. can you ask your administrator to open up a support case for this?
To help you understand the Zarafa architecture, a schematic presentation of Zarafa’s technical structure is shown here. When you want to install Zarafa, you can see here how the Linux server and Zarafa are integrated, as well as how Zarafa collaborates with Windows and Outlook.
There is a more extensive description of this model available in the Server manual, section 1.2.