yeah free anti-spam software will reward you with spyware or adware.
there is at least one company that will auto reply to incoming emails with a request to reply back by clicking a link. This causes that person to get added to your whitelist, proving it's a real person and not some spam. Only after that do the emails from that person get delivered to you.
I believe something like this should be scriptable in outlook, but maybe not. If you have a linux machine or something that is running a mail server of some sort, there is code out there for free that will handle this for you in this manner. In that case you'd use this mail server as your mail server in outlook, and it would be configured to check mail on the actual mail server.