forw: 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/forw - from package: mailutils-mh
/usr/bin/mh/forw - from package: nmh

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

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