rt-email-group-admin: 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/rt-email-group-admin - from package: rt3

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

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