Where do I find the Merchant Post URL value that I need for merchant notifications to work from my Cybersource account?

PRESSERO > *Pressero FAQs
Go to the Pressero site you have Cybersource activated on as a payment method. From the Settings window, go to the Payment Methods tab. Click on the Cybersource payment method that you have enabled on the site. Any enabled payment methods on the site will show in green on this area. Scroll down to the Post Back URL setting. That url address value should be used as the Merchant Post URL on your Cybersource account.