mservdetect: 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/bin/mservdetect - from package: masqmail

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