OpenExchange: Sync to outlook

Hi.
I am in the middle of an unfriendly takeover:  A customer has a disagreement with his former IT-guy.  He refuses to hand over any documentation.
I am in the process of installing a new Windows-based network at the customer's site.  Right now I try to export all content out of the OpenXchange mailboxes to PSTs.

Most users used to work with Outlook.  They were easy.
The boss is using a Mac.  It was connected to OpenXchange via iMail + IMAP.  On his iPhone he used Exchange ActiveSync.  His Calendar and Contacts used to sync fine.
All the content is visible also in the web frontend (http://192.168.1.1/ox6/ox.html)

In order to retrieve the data, I connected Outlook OXtender2.  The folders are shown, including all address books and calendars.  Now after about 5h of syncing, the status of OXtender shows "Ready".  It does not seem to do anything anymore, CPU and network usage are zero.
Some of the mail folders have content, others do not.  The main contacts folder shows no content, another (unimportant) contact folder was synced.  Half of the calendar content is missing.

There is no error message.  All content can be viewed just fine in the web frontend.

While I can manage with all mail folders using IMAP to sync the content and export it out, I'm out of ideas concerning contacts and calendars.  
Does anybody have an idea?

I am in posession of root access to the hosting server, but have no passwords to any other administrative consoles or programs.

Thanks a lot,
Ralph