There is a post on the Able forum about this and it has some quotes from Paypal saying IPN is a problem. IPN is what the normal Paypal button uses, not Paypal Express or Payflow Pro
I've been round & round with PP Merchant Tech Support, finally they have admitted that the IPN system just isn't reliable - got this in an email from them this morning:
I would also like to acknowledge that, it is true that IPN is not fully reliable. It is highly possible that there would be delays in sending the IPN messages at certain times( due to various reason : connectivity, high volume of payments) .
IPNs acts as a message which is to notify you when a payment occurs, however it is not used as a real -time system notification message. You may refer to this documentation : https://developer.paypal.com/docs/class ... /IPNIntro/ . It has explained that, IPN would encounter delays and it should not be treated as the only payment notification mechanism.
Therefore, the best way to get immediate payment notification is by API response message. When your website sends us the payment details in the form of an API request, PayPal immediately processes the payment and notify your backend through API response ( whether the payment is success / failure ). In your case, yes PayPal Payflow PRO does uses the API to process payments and you should be able to receive PayPal payments as well through the Hosted Checkout pages. Also, you can still implement the IPN function, however just not as the only logic system to update your payment notifications.