mhpath: 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/mhpath - from package: mailutils-mh
/usr/bin/mh/mhpath - from package: nmh

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

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