horde-remove-user-data: command not found

Have You tried accessing the binary with the full path?

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

[root@server ~]# echo $PATH

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-remove-user-data - 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-remove-user-data - from package: php-horde

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