The reason you don't need to worry about the redirects is because your users will never be visiting this page, this page is only used after a transaction has been placed, it will get the IPN post from PayPal but your users will never go here.
The next part of this will be to send out the email on the IPN page, when you submit a test IPN post to this page you should receive the email receipt with all the details in it. You can also check that this page is doing things properly by checking the database if you are updating the status of the order. You should see the updated record after the IPN post makes it to the page.
You can test this out using the sandbox, it will help you get past any errors or issues on the page. As a final test though you should take it out of the sandbox and run a live test transaction. You can then login to PayPal to check the transaction and cancel it.
