formmailtest: 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/formmailtest - from package: dsbltesters

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

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