mailtool: 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/mailtool - from package: cone

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

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