reject: 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/reject - from package: cups

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

On Debian possible default full paths are:

/usr/sbin/reject - from package: cups-client

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

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