Do I need to enable IPN on PayPal

[buns1525]

Hello - I have the latest version of zen cart installed for my client. I have the Paypal Express Checkout module enabled and it is working well for them. On the PayPal side, he has enabled IPN and set the return URL to https://www.theirwebsite.com/cart/ipn_main_handler.php

They have received an email recently, telling them that the IPN has been failing (listed below). I've seen it stated that IPN was the old "PayPal Standard" way, and that Express Checkout is the new way. My question is, since we are using Express Checkout, and since we are not doing any back office processing (I have not made any modifications to ipn_main_handler.php), do we really need to use IPN? Can we safely uncheck that in PayPal? Everything is working for them. They are receiving payments. The customer is taken back to the checkout page. Is the IPN setting necessary? Will it break the process if I have him uncheck it? Do I need to leave it checked and update the ipn_main_handler page in some way?

Paypal Email:
Please check your server that handles PayPal Instant Payment Notifications (IPN). IPNs sent to the following URL(s) are failing

Thanks in advance.

[DrByte]

"Do I need to enable IPN on PayPal?"
Short answer: no. But ... you might want it anyway. Read on...


A bit of background:

1. Strictly speaking, "IPN" is not a payment module. IPN stands for Instant Payment Notification. It is a subsystem that PayPal added to their products to allow websites who used the old-style/legacy/archaic methods of doing transactions to be notified that a payment was made and to do something about it.
It was basically a bandage to fix the many shortcomings of their older tools when newer ecommerce technologies were introduced to the internet.

2. PayPal Payments Standard is that old "product" that PayPal offered so stores could put "a button" on a product's HTML page and customers could click that button and add it to their "cart" (an index on the paypal end of the things the customer indicated they'd like to buy). Customers would then make their purchase by logging into PayPal and completing payment.
The "cart" at PayPal was very limited in the features it could support.

3. For many years this "Standard" product existed in isolation, but people pressured PayPal to make it more useful for database-driven sites. So, the IPN was added to tell database-driven stores that a purchase had been completed and funds deposited into the merchant's PayPal account. PayPal also added the ability to have the database-driven store build its own list of things the customer wanted to buy, and submit them in aggregate to PayPal who merely collected payment instead of also being just a basic rudimentary shopping cart.

4. Enter merchant demand for stores like Zen Cart to accommodate both aspects of these technologies, and so the "PayPal IPN Payment Module" was introduced ... which was a hybrid response to the only option PayPal offered at the time: customers shop in Zen Cart, and Zen Cart hands the customer off with an aggregate cart to PayPal. But PayPal's system couldn't tell the store that the payment was accepted, unless it sent an IPN. So, stores like Zen Cart added accessories like ipn_main_handler.php to receive those notices. And, when an IPN was received it would respond with a request to verify that it was legitimate, and once validated it would be matched up with the (sitting-in-limbo) order in the store, and push that order into the list of completed/paid purchases.
This background IPN would sometimes get lost or fail to validate, or never arrive, depending on whether PayPal's servers were too busy, or a security conflict occurred, or a firewall error blocked it, and so on. Many headaches while waiting on a better technology to be offered by PayPal ... something that would give the store real-time confirmation/notification of an order.

5. Then PayPal decided to catch up with the times and introduced Express Checkout. This was very different and much more reliable. It allows customers to shop on the store, submit detailed items to Paypal, collect payment, receive immediate approval of payment, and store the order immediately into the system (just like many regular credit card gateways have done for decades). With this newer technology, there was no need to wait for an IPN to tell the store that a payment was made, because that information was provided in real-time, immediately.

6. However, PayPal has always allowed IPNs to be sent for "transaction status updates", such as voids, refunds, auth/capture, echecks-cleared and so on. It is for these status updates that keeping the "IPN" and "IPN Notification URL" enabled on your site is useful.
In this respect PayPal offers something that most regular credit card gateways do not.

If you don't care whether your store is notified of these changes to an order, then you can turn the IPN feature off on your store when using Express Checkout.

If you want to keep that feature, then you'll need to troubleshoot why the IPNs are failing to be delivered or acknowledged (ie: your store sends back a validation request). There are some tools available to troubleshoot IPN concepts in general:
- click the URL to ipn_main_handler that's in your email you got from PayPal. What happens? If you get a completely blank page, there's a clear problem.
- guidelines http://www.zen-cart.com/wiki/index.php/PayPal
- communication testing tool: http://www.zen-cart.com/showthread.p...634#post373634

[buns1525]

Thanks Dr. Byte. I think I'll still look to troubleshoot it a bit, but at least now I have a much better understanding. I really appreciate it.