SpamGuard Plus is a feature that automatically filters suspected spam to your Spam folder. SpamGuard Plus also learns specifically what you consider spam and not spam, and filters those messages to the appropriate folder. The more you train the filters by marking messages as Spam or Not Spam, the better the filters will work for you.
If you have a Business Email address associated with a Yahoo! ID SpamGuard Plus is active by default. You can confirm and manage SpamGuard settings in the Business Email Options:
Business Email Options Link
Business Email Options Pull-Down Menu
Business Email Options General Link
Business Email Options SpamGuard Checkbox
Business Email Options: Empty Spam Folder Pull-Down Menu
Business Email Options: Show Images Pull-Down Menu
Note: This feature is not available to users with POP-only email addresses.