How do I use Spam Guardian?
To try Spam Guardian, log in to Plesk - click on your domain name, then click on the "Spam Control" button.
Then a list of email boxes for that domain come up, and you click the check box under "Protect" and then click "update"
Or you can click to protect the entire domain (probably better)
You can tell it to forward spam to you - do this for just while and you can get a feel for what it's marking as spam. There is a "Help" button with more detailed instructions. It's a little complicated.
Basically if you change that number that's currently "10" to lower, the SG is more aggressive and you risk losing good mail. If you set it to higher than 10, you let more spam through.