PayPal Changes: Updated IP Addresses

If your store is configured to use the PayPal Website Payments Standard module for accepting payments (formerly also called "PayPal IPN" module), then this notice applies to you.

If your server has had to be specially configured to allow IPN traffic to/from your server in order to process payment notices, you'll need to have your hosting company open up the additional new IP address PayPal is adding effective April 7, 2011 https://ppmts.custhelp.com/app/answers/detail/a_id/92

This is a good time to remind you that you really should be using PayPal Express Checkout if you're accepting PayPal on your site. Using the old IPN/Website-Payments-Standard method for payments is becoming antiquated and has been known to have problems in various circumstances. Using the newer Express Checkout approach is far more reliable for completing payments and giving your customer up-to-date confirmation that their order has been paid and accepted by your store.
Naturally, also upgrading to the latest version of Zen Cart is similarly valuable and important.

PayPal is sending the following reminder messages out to their merchants.
If you are using Express Checkout or Website Payments Pro with Zen Cart, you will not need to make any changes.
If you are using WPS - Website Payments Standard, aka PayPal IPN, you will need to follow the instructions I posted above.

We recommend you use Express Checkout for more reliable transaction processing, and a more seamless customer checkout experience.

PayPal:

Over the course of the week, we will be moving some of our processing services to a new state-of-the art data center. As a result of this move, you may need to make networking and/or firewall updates. If you hard code your IP addresses, you'll need to update your systems with the new IP addresses to avoid a service interruption should we switch to back-up mode.

Updated List of IP Addresses

If the new IP addresses are not recognized by your system, it could result in the inability to process transactions if we revert to the back-up server. For the updated list of IP addresses used by PayPal.com, please refer to the Merchant Technical Support FAQ: IP address for PayPal servers. We recommend that you subscribe to this list so you can receive automatic notifications of any changes to the IP addresses for our servers.

If you are unsure of the type of authentication you are currently using or if you would like to confirm if you will be impacted by this change, we recommend contacting your web developer or IT Department regarding this notification.

If you or your developer requires technical assistance regarding this update, you may file a ticket with Merchant Technical Services. https://www.paypal.com/mts

Our guiding principle is to do everything we can to help you succeed. We believe that the new data center will do that by improving our services and capabilities. We appreciate your patience as we conduct this transition.

Sincerely,

PayPal