[Exim] Relay after SMTP authentication

Hi,

i want to configure my exim4.12 to permit relay only after smtp authentication, but i not found the parameter to set this...
how can i implement?

thanks,
--
Bruno Couto do E. Santo.
Analista de Suporte - Linux Solutions - http://www.linuxsolutions.com.br
Tel.: +55 (21) 2526-7262