amavisd-new-cronjob: 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
/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/sbin/amavisd-new-cronjob - from package: amavisd-new

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