The Simple Commerce Module and PayPal’s IPN (Instant Payment Notification) allow you to fully integrate PayPal with your store, automatically keeping track of purchases, and sending notification emails to both administrators and customers.
PayPal’s Instant Payment Notification service processes transactions on their server, and notifies ExpressionEngine when the transaction is complete, so purchases are not recorded in your store until they are finalized.
Note: While you can still use Simple Commerce generated PayPal links to sell items to users browsing your site as guests, the Instant Payment Notification features, such as transaction recording and email notifications, will only work for purchases made by logged-in members of your site.
Note: In order for PayPal to be able to send payment notifications to your site, your site needs to be online and accessible to the public. If anything would prevent an unauthenticated user from visiting your site, PayPal will be unable to send payment notifications.
Please refer to PayPal’s instructions for the latest information. To enable Instant Payment Notification, login to PayPal, and select “Payment Notifications” from the Profile submenu. Provide PayPal with the Instant Payment Notification (IPN) URL found in the Simple Commerce preferences.
Note: For ExpressionEngine to reliably track PayPal transactions within Simple Commerce, you must enter your primary PayPal email address as the PayPal Account in the Simple Commerce preferences.