Create a Fail-safe script for Paypal Checkout

We have a Flash shopping cart that uses paypal to process payments. The shopping cart is designed to send an email with links to the buyer upon completion of payment but about 10% of the time they never receive the email or links at the instant download page they are taken to after paypal. I'd like to have a fail-safe script written that can check an inbox for paypal receipts possibly via cronjob and match them to customers, and if it notices that the database still has the customer marked as "NOT PAID" then it marks it paid and sends the email with the links. This is the best option I can think of as another coder already has tweaked the code to make it fail-safe but it has not worked completely. Though it did improve. I'm open to other options other than my suggestion as well. This is the shopping cart [login to view URL] ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform Linux