opendkim-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 Debian possible default full paths are:

/usr/bin/opendkim-spam - from package: opendkim-tools

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

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