sievec: 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/sievec - from package: dovecot-pigeonhole

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

On Debian possible default full paths are:

/usr/bin/sievec - from package: dovecot-sieve
/usr/lib/cyrus/bin/sievec - from package: cyrus-common

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

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