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

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

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