mail-files: 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/mail-files - from package: sharutils

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

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