test-filter-module: 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/test-filter-module - from package: courier-filter-perl

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

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