got that problem solved
did forget to add my roundcube server to the relay servers list
does anyone know how to make it possible to see the mails i sent in roundcube in the "sent mails" directory on the exchange?
i see them only in the roundcube sent folder not when i login to the exchange by the webinterface of it or in outlook
it looks like the mails are only stored lokal in the roundcube db and sent via anonymous so the exchange does not know it comes from the user
so what login data do i have to choose?