Nothing will stop spam from being sent to you, it's a matter of how you deal with it.
Personally, I like the way Mozilla and Mozilla Thunderbird handle spam. They use an adaptive filter which "learns" based on experience what is and isn't spam. It's never 100% accurate, but then no spam prevention method is that doesn't bring it's own set of headaches. So you can set it to move all suspected junk mail to a special folder, where you can peruse through it at your lesisure to make sure everything in there is indeed spam.
Most of the other options try to delete the mail as it comes in, but I'm always worried about the false-positive problem. Being that a non-spam message is flagged as spam, and deleted. I'm not willing to take that risk, but if you are, you can look into those solutions.
is there any strong anti-spam application, for free