Actually, you can just disregard PayPal IPN settings. Our Cart and Buy Now buttons transmit our IPN requirements to PayPal for every order, which would override any manual IPN settings in your PayPal account (such as those you'd entered for your previous ecommerce service provider). This help page covers the only settings you'd need to use PayPal with E-junkie:
BTW, although our current Admin panel offers a "PayPal Cart" version of button codes, those buttons are NOT necessary if you simply want to accept checkout payments with PayPal. They also no longer work correctly in many ways due to recent changes at PayPal's end that we have been unable to work around, so we're removing that version of button codes from the next version of Seller Admin. We would recommend using our standard E-junkie Cart button codes, which will show buyers a PayPal checkout button in the cart, or use our Buy Now buttons which bypass the cart to take buyers directly to instant checkout with PayPal for just one item at a time.
Our Getting Started help page is a good place to begin setting up with E-junkie: