horde-pref-remove: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/horde-pref-remove - from package: php-horde-horde

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/horde-pref-remove - from package: php-horde

You may install the required package with command apt-get install {package}

Error in other languages:
horde-pref-remove: bevel nie gevind nie
horde-pref-remove: comandă negăsită
horde-pref-remove: comando não encontrado
horde-pref-remove: commande introuvable
horde-pref-remove: command not found
horde-pref-remove: käsku ei ole
horde-pref-remove: không tìm thấy lệnh
horde-pref-remove: komanda nerasta
horde-pref-remove: Kommando nicht gefunden.
horde-pref-remove: kommandot finns inte
horde-pref-remove: komut yok
horde-pref-remove: nie znaleziono polecenia
horde-pref-remove: níor aimsíodh an t-ordú
horde-pref-remove: no se encontró la orden
horde-pref-remove: no s'ha trobat l'ordre
horde-pref-remove: opdracht niet gevonden
horde-pref-remove: parancs nem található
horde-pref-remove: perintah tidak ditemukan
horde-pref-remove: príkaz nenájdený
horde-pref-remove: příkaz nenalezen
horde-pref-remove: команда не найдена
horde-pref-remove: командата не е открита
horde-pref-remove: 命令找不到
horde-pref-remove: コマンドが見つかりません