postal-list: 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/postal-list - from package: postal

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

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