mailbot: 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/mailbot - from package: courier-maildrop
/usr/bin/mailbot - from package: maildrop

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

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