sb_mboxtrain: 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/bin/sb_mboxtrain - from package: spambayes

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