gmtp: 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/gmtp - from package: gmtp

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

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