Paypal Standard is an off-site payment gateway that allows your customers to securely pay for their orders at the checkout. As the transaction occurs from the Paypal website and not at the checkout page unlike on-site payment gateways, dealing with Paypal Standard therefore requires a few more configuration work from you.
The configuration is done at two levels: the WebStore Manager (WSM) and in your Paypal account. Both of which were covered in this blog post: https://www.nitrosell.com/blog/paypal-payment-standard-update-3665.html Briefly speaking, you will need to have the Auto-return feature enabled in your Paypal account as well as the Instant Payment Notification (IPN). In the WSM, you will need to enter your API credentials. These are needed to make the necessary requests to Paypal, not only when you are using the delayed capture but also on a daily basis, we make calls to Paypal to get the latest transactions that you received on that day. We then compare it with what we have in your file and if an order is missing for any reason then it is added at that point. It should be noted that Paypal only returns the latest 100 transactions that you received.
When enabling the IPN and the Auto-Return, Paypal will ask you to specify a URL which is in this form: https://secure1.nitrosell.com/WEBSTORE_URL/store/go/checkout-callback/8/ where WEBSTORE_URL is the live URL of your web store. For instance, it can look like this: https://secure1.nitrosell.com/www.mywebstore.com/store/go/checkout-callback/8/ We automatically compute the correct URL at the checkout before sending the request to Paypal so you shouldn’t worry if you made a mistake while typing that address.
IPN calls are initiated by Paypal whenever a new action is registered on a transaction. One of which may be to inform us that the transaction has been cleared and at that point, we insert the order in your database.