The best place to turn for assistance with Horde applications is the support staff at the Internet service provider, school, company, or other organization whose webmail service you are using. Many commonly-encountered problems involve local matters with which Horde developers cannot assist you.
If you are not able to obtain assistance from your local support staff, you may wish to try asking the mailing list for the component you're using. Make sure you describe the problem clearly, including all error messages you might have received. Remember to report the version number of the application (if you know it), as well as what browser and OS you are using to access it.
Please don't contact the developers or the FAQ maintainer directly. They usually don't have time to deal with individual installations of Horde and its components, being too busy developing and FAQ-maintaining. (Besides, they're probably on the mailing list anyhow.)