If you are unable to fix Spam filter issue in your Yahoo account, try fixing the problem by following these steps:
• Sign in to your Yahoo account and locate the spam email.
• Right-click on the spam email and select This is Spam option from the drop-down list.
• Alternatively, if you are getting spam messages from a particular email address, you can block the email address of the sender.
• To block email address go to Gear icon > Settings > Blocked Addresses.
• Enter the email address of the sender in the Add an Address field and click Block.
• Click on the Save button to apply the changes.