sieved: 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/lib/cyrus/bin/sieved - from package: cyrus-common

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

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