qbiff: 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/qbiff - from package: qmail
/var/lib/qmail/bin/qbiff - from package: qmail

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

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