I'm currently testing my web app which uses PayPal's IPN mechanism. This is my set up:

- I have created a Personal and a Business test account in my PayPal developer account.
- The web app is deployed to my Shared Hosting server.
- My local browser is logged on in the PayPal Sandbox with my PayPal developer account.

Now I point my local browser to the web app and initiate the payment (single payment/express, no cart). The Sandbox's payment pages appear, I complete the payment and I'm redirected to my 'redirect' URL. So far no worries.

Behind the scenes, PayPal invokes my 'notify_url' URL to tell the web app that a transaction has been completed. Now, my web app calls https://www.sandbox.paypal.com/cgi-bin/webscr with the 'cmd' parameter set to '_notify-validate', to protect against faked transactions. It expects PayPal's server to return 'VERIFIED' if the transaction exists.

At this point, my web app does not receive 'VERIFIED', but a generic HTML page with the message "Please login to use the PayPal Sandbox features". I understand why I'm getting this answer. My local browser is logged in on PayPal's Sandbox, but the HTTP client on my web server is not.

But how can I log it in?

Thank you!