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

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

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