I was able to configure Postfix + SASL2 with the following lines in
main.cf:
smtpd_recipient_restrictions = permit_sasl_authenticated,
permit_mynetworks,
reject_unauth_destination,
reject_non_fqdn_recipient,
reject_rbl_client list.dsbl.org,
reject_rbl_client relays.ordb.org,
reject_rbl_client zombie.dnsbl.sorbs.net,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client bl.spamcop.net,
reject_rbl_client sbl.spamhaus.org,
reject_rhsbl_sender dsn.rfc-ignorant.org
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain =

but...as this is a relay for a exchange server, it does not
authenticaete with user/password of the active directory, I must type a
real unix user/password so it can send mail.
Any idea on how to glue this with the active directory?

regards,
-eduardo s.m.