visit URL after order is placed

after the customer place an order I need to visit URL for external tracking.

URL should be in this format:

http://www.externaltracking.com/order.php?id=12345
&[email protected]&product[]=Product1&product[]=Product2&product[]=Product3...

where [email protected] is an email of customer
and Product1, Product2, Product3, ... are products that he bought (can be any amount  of products)

after visiting this URL, if server reply OK everything was correct

can you help me implement this feature? thanks a lot.

Look at the implemenation of other similar payment methods (e.g., PayPal Standard, 2Checkout). In most cases all you need to support such payment gateways (with redirection to a third-party site) is to implement PostProcessPayment method if IPaymentMethod method.