NEWBIE: Needing Help

Hello

I am fairly new at the Postfix environment. I have been told to setup
a Postfix Mail relay for our internal MS Exchange Server. There is
alot of documentation out there for setting a mail relay up using
Postfix, but little about outbound relay IMO. I have the mail relay
working from external mail(internal), it works perfectly. When I send
internally, from the MS Exchaneg server, it bypasses the Postfix
server. Is there something I am missing, or if the relay is setup,
should it just work.

I will be installing SpamAssassin also, along with amavisd-new and
Clam AV. Are there any direct to the point tutorials on installing and
configuring from a newbies point of view. I installed SpamAssassin,
but nothing is being filtered.

Thanks for the help, I appologize if the answers are here already, I
have been searching and have had no luck

Thank You
BossCaper