list_members: 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/list_members - 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/list_members - from package: mailman
/usr/sbin/list_members - from package: mailman

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

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