kmail_antivir.sh: 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/kmail_antivir.sh - from package: kdepim

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

On Debian possible default full paths are:

/usr/bin/kmail_antivir.sh - from package: kmail

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

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