@morrow without logs this will be hard to track down. can you ask your administrator to open up a support case for this?
There are three different user plug-ins for Zarafa; the UNIX, the LDAP and the internal DB plug-in:
* The UNIX plug-in uses information from /etc/passwd, /etc/group and /etc/shadow. This means that only the Linux users can get access to Zarafa. By setting a uid range of wich users are added to Zarafa. In the same way you can add groups to Zarafa. Users with a special shell (default /bin/false) will be added as non-active user. With the Unix plug-in is it necessary to add additional information like email address, admin option and user quota settings in the database. This information needs to be added to the database with the Zarafa-admin tool. The uid would be stored in the data to make a link between the Linux users and the information in the database.
* The LDAP plug-in uses information from a LDAP or ADS server. All information about users, groups and membership can be retrieved from the LDAP or ADS server. The managing of the users and groups has to be done in LDAP or ADS. Only the uid would be stored in the Zarafa database, other data would receive from LDAP or ADS.
* The DB plug-in would be installed by default and need no more configuration. All user information would store in the database. The managing has to be done with the zarafa-admin tool.