I have just verified some PayPal Updates that some people may like to know.

IPN Verification Postback to HTTPS If you are using PayPal’s Instant Payment Notification (IPN) service, you will need to ensure that HTTPS is used when posting the message back to PayPal for verification. After June of 2017 HTTP postbacks will no longer be supported.

"At this time, there is no requirement for HTTPS on the outbound IPN call from PayPal to the merchant’s IPN listener. ... To avoid any disruption of service, you must verify that your systems are ready for this change by June 30, 2017"