readmsg.mailutils: 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/readmsg.mailutils - from package: mailutils

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

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