I recently started getting these emails from Paypal as well, and not sure how to respond. I'm using PP WPPro with UC and have processed a few orders without any hitches. Since WPP doesn't even use IPN, I suspect something has changed on PayPal's side and they want to ping a specific URL to ensure the IPN works.

I'm going to do nothing for now and see what happens. I'll post an update after getting my next sale. Please share your experiences if you have any. Thanks.