Using OS X Mail?

1. Select New Mailbox... from the Mail menu.
2. Type in a mailbox name (for example, spam).
3. Select Preferences... from the Mail menu.
4. Click on the Rules icon (top right) and then the Add Rule button.
5. Type in spam for the description.
6. Pull down the menu which reads From and select Edit Header List....
7. Enter X-Spam-Flag in the Header: text field.
8. Click Add Header and then OK.
9. Pull down the menu again and select the new X-Spam-Flag option.
10. Type YES in the text field (full line: X-Spam-Flag Contains YES).
11. Select spam from the No mailbox selected pull-down menu.
12. Click OK and close the Preferences window.