mhl: 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/mu-mh/mhl - from package: mailutils-mh

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

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