rpost: 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/rpost - from package: suck

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

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