Write some Software to track sales

Here is my issue. I get referral enquiries via a 3rd party that expects me to give them commission on all successful orders. I using their email send the customer details. Some are successful, some are not. I currently advise which are and they want more transparency. Im looking for ideas in order to do this. are there any email linking systems that we can develop so that if a successful email is sent to an address that was sent by the 3rd part then automatically they would be notified? Any ideas?