Configuring Trusted SMTP Relay in Exchange on SBS 2008

Here are instructions for creating an SMTP relay on SBS 2008 (remote clients who don't use Exchange that you want to send through the Exchange server via SMTP with authentication):

http://blogs.technet.com/sbs/archive/2008/09/18/how-to-configure-trusted-smtp-relay-in-exchange-on-sbs-2008.aspx