Hey There,
Honestly, You might be best off with an easier single-service config using just your postfix mta.
http://www.howtoforge.com/virtual_postfix_antispam Is pretty good for getting going.
Spamd is pretty resource intensive when you are getting a good amount of spam to check. The benefit of spamd vs. just configuring rbl lookups in your MTA is that you are centralizing all spam lookups to a single service and offloading that from your MTA to allow it to do its job: Transport Mail. Also, Spamd being its own service allows for separate spamd servers.
If you are only trying to do RBL Lookups, just configure it in your MTA. However, don't count spamd out just yet. It is pretty nice and has tons of other plugins (Like Razor and Pyzor).
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Michael Piekarski
Network Engineer
mpiekarski@hostmysite.com
www.hostmysite.com