dnsenum: 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/dnsenum - from package: dnsenum

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

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