C# with PayPal Donate needs IPN and Mail to payer

There is a PayPal Donatebutton in a C# Form. Existing PayPal button action: var url = "[login to view URL]" + @"?cmd=" + "_donations" + @"&business=" + "mypaypal-mail" + @"&lc=" + "US" + @"&item_name=" + "Marlin 3D printer Tool Donation" + @"&amount=5" + @"&currency_code=" + "USD" + @"&bn=" + "PP%2dDonationsBF"; (Missing IPN link) Existing MANUAL License tool.. When I get the PayPal mail I enter name and email in my C# license tool A mail is sent to the Donator: (In this case I sent it to myself) ============================================================== Thank you for your donation! This license key will remove the Demo mode of the Marlin3DprinterTool This is the licenseKey for Marlin3DprinterTool efXInRhvedmyuc+y3holjgQ6sgP1gZvnv1HfZq2bk3mrf/ofMVLfdwSCrjzSaFd74D5ZtztpFxQt8XtlaqUMJfrYwUx8sSUsNX5jZlZirFASDPSVvYz8RTyFqGIwffFxjmlb89bdXPGVU9fTl0VeBHndc+3u2HRfSAQWinytr+KbCfLUEqlTXe3qjvQXkiQT Copy the key and paste it into the Marlin3DprinterTool setup MANY REGARDS! Johnny ============================================================= After the mail is sent the data behind the Base64 string is appended to a file The file with the donators look like this: ------ dawid86szewczyk(a)[login to view URL] ;Dawid Szewczyk ;License created:2017-03-19 16:46 winkboyer(a)[login to view URL];Bill Boyer ;License created:2017-03-21 07:09 [login to view URL](a)[login to view URL] ;Paul Curutiu ;License created:2017-03-21 07:11 pauldesmet45(a)[login to view URL];Paul De Smet;License created:2017-03-21 11:13 RanchoMattPS(a)[login to view URL];Matthew Dodd ;License created:2017-03-25 15:19 rtwallner(a)[login to view URL];Ron Wallner;License created:2017-03-27 09:37 ----- Its the same string that created the Base64 Attached is the C# License tool The project is to make this automatic. * Add IPN to PHP page ([login to view URL] * Verify IPN * Get the name and Mail-adress from the IPN * Create mail to payer with CSV with name and email as a Base64 (=license-key) * Save the name and email in a file and/or MySQL database Here is example of code: [login to view URL] [login to view URL] [login to view URL] [login to view URL]