mlmmj-unsub: 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/mlmmj-unsub - from package: mlmmj

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

On Debian possible default full paths are:

/usr/bin/mlmmj-unsub - from package: mlmmj

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

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