smsbox: 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 Debian possible default full paths are:

/usr/sbin/smsbox - from package: kannel

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