spam: 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/spam - from package: opensp

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

On Debian possible default full paths are:

/usr/bin/spam - from package: sp

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

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