clamd.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/clamd.amavisd - from package: amavisd-new

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

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