sieve-dump: 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 CentOS possible default full paths are:

/usr/bin/sieve-dump - from package: dovecot-pigeonhole

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/sieve-dump - from package: dovecot-sieve

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

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