When you have navigated to the Anti-Spam homepage (Services > Anti-Spam), click on the Detection Settings tab.
The first option you can chose is if you wish to use the approved senders list which you would have set up. This can be either the IP or Domains and e-mail address only or use both of them. You can assign to use the SPF function which explains what it does next to the ticket box.
The following option allows you to choose how Symantec will deal with the spam mail and this can be by the option in the drop down box.
You have the option of using the Skeptic Heuristics which is part of Symantec which checks everything in the mail header to make sure the mail has come from the right location. You can also choose how Symantec deals with this mail.
In the Subject Line Text section, you can customise how the subject line will appear for emails tagged as spam.
If you change your settings to quarantine spam emails, the intended recipient will be sent an email informing them that an email is in quarantine along with a link to view the email.