mailplate: 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/mailplate - from package: mailplate

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

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