Just got a notice about changes to the post back from IPN from PayPal.
Merchants and partners use Instant Payment Notification (IPN) to receive notifications of events related to PayPal transactions. The IPN message service requires that you acknowledge receipt of these messages and validate them. This process includes posting the messages back to PayPal for verification. In the past, PayPal has allowed the use of HTTP for these postbacks. For increased security going forward, only HTTPS will be allowed. To avoid any disruption of service, you must verify that your systems
are ready for this change by September 30, 2016