mxallowd: 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/sbin/mxallowd - from package: mxallowd

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

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