sieve-test: 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-test - 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-test - from package: dovecot-sieve

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

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