smtpfront-qmail: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/smtpfront-qmail - from package: mailfront

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