Yes, Yahoo! Business Email offers the following ways to help you block junk mail:

If you receive multiple messages from the same source and would like to block the sender, you can set up a filter to match some unique part of the sender's address. Generally a name or a phrase in the body of the message works well, but as long as the sender always uses the same mailing address, filtering based on the Sender: field is very effective. Just set the destination folder to Trash.

Note: Using filters to avoid unwanted mail doesn't actually prevent it from being sent.

You can also use the "Blocked Addresses" feature to automatically delete a sender's messages.

1. Sign in to your Yahoo! Business Email account.
2. From the main Yahoo! Business Mail page, click the Tools (gear) icon link in the upper-right corner of the page.
   
   Business Email Tools (Gear) Icon
3. Select "Mail Options" from the pull-down menu.
   
   Business Email Tools Pull-Down: Mail Options
4. Click the "Blocked Addresses" link located in the left column.

   
   Mail Options Menu: Blocked Addresses

5. Enter the address or domain you would like to block in the "Add a blocked address" field and click the Add (+) button to add the address to the blocked addresses list.

   
   Blocked Addresses: Add an Address

Yahoo! Business Email allows up to 500 blocked email addresses. Learn more about avoiding spam.