rmf: 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 Debian possible default full paths are:

/usr/bin/mu-mh/rmf - from package: mailutils-mh
/usr/bin/mh/rmf - from package: nmh

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

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