In addition to this very document (Kerio MailServer 6, Administrator's Guide), other documents are also available for Kerio MailServer, namely Kerio MailServer 6, Step-by-Step Guide (information on server installation and basic configuration) and Kerio MailServer 6, User's Guide (detailed information on configuration and use of client applications and the web interface used for connection to the server).
Besides the documentation, you can also target various issues by referring to:
Product forum — in this discussion, you can encounter experience and problems of other administrators using the same product. You may find a working solution for your issues here.
Knowledge Base — here you can find a set of articles troubleshooting particular problems.