qmqp-source: 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/qmqp-source - from package: postfix

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

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