pysieved: 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/pysieved - from package: pysieved

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

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