Steps to install horde in plesk
Before starting please make sure you have backups of you plesk database.
cd /root
mysqldump -u admin -p`cat /etc/psa/.psa.shadow` psa > psabackup.sql
Go to plesk admin binary folder
[root@admin ~]# cd /usr/local/psa/admin/bin
Then run auto installer with install component horde
[root@admin /usr/local/psa/admin/bin]# ./autoinstaller –select-release-current –install-component horde
That’s it. You have installed horde in your plesk panel.
Reference: http://logicsupport.com/blog/?p=240