forward: 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/forward - from package: qmail
/var/lib/qmail/bin/forward - from package: qmail

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

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