way to eliminate 4,000 yahoo emails?

Omgyme's answer is right

Sorry, but you can only delete one page full at a time. Expand your Email page to Delete more at a time. 1. Click on the the Options link in the upper right of your Yahoo Mail page. 2. Click on "General Preferences." 3. Go to the "Message Results per page." 4. Click the down arrow and select 200 (maximum) as the number to show per page. 5. Go to the bottom of this page and click the Save button. First do this for the first page, for those that you received before that date, and check the box next to them, go to the top and click the Delete button. Now, at the top of each In-Box page, that comes after that, check the Sender box at the top, then click the Delete button. There goes the first 200. Do this for each page that opens after that.