dspam_clean: 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/dspam_clean - from package: dspam

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

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