Where can I customize or upload a theme for Horde Webmail?
The theme files are located in /usr/local/cpanel/base/horde/themes
Please note cPanel handles the updates for this RPM; any customizations will be overwritten. Instead, we suggest building a custom version of the RPM. How to Build and Install Custom RPMs
# rpm -qa |grep horde
# rpm -qf /usr/local/cpanel/base/horde/themes