Supporter and Paypal IPN errors after changing main site URL

A few months ago, we changed our main site URL, and I thought we changed everything in our multi-DB setup to point to the new main site URL. (All links from OLDSITE.com have been changed to NEWSITE.com)

But we're now getting Supporter IPN error messages from Paypal pointing to the OLD URL instead of the new one. Is there a file or data field somewhere in Supporter where we put in the main site URL?

Or is this a problem on Paypal's end?

--EMAIL MESSAGE FROM PAYPAL--
Please check your server that handles PayPal Instant Payment Notifications (IPN). IPNs sent to the following URL(s) are failing:

http://blog1.OLDSITE.com/supporter-paypal.php
http://blog2.OLDSITE.com/supporter-paypal.php
http://test.OLDSITE.com/supporter-paypal.php

If you do not recognize this URL, you may be using a service provider that is using IPN on your behalf. Please contact your service provider with the above information. If this problem continues, IPNs may be disabled for your account.

Thank you for your prompt attention to this issue.

Thanks,
PayPal