PayPal is upgrading the certificate for [url removed, login to view] to SHA-256. This endpoint is also used by merchants using the Instant Payment Notification (IPN) product.
This upgrade is scheduled for 9/30/2015; however, we may need to change this date on short notice to you to align to the industry security standard.
You’re receiving this notification because you’ve been identified as a merchant who has used IPN endpoints within the past year. If you have not made the necessary changes, we urge you to do so right away to avoid a disruption of your service!
Merchant Security System Upgrade Guide. In addition, our 2015-2016 SSL Certificate Change microsite
Helpful link explanation is shown below: