mmsitepass: 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/lib/mailman/bin/mmsitepass - from package: mailman

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

On Debian possible default full paths are:

/usr/lib/mailman/bin/mmsitepass - from package: mailman
/usr/sbin/mmsitepass - from package: mailman

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

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