Just looked this up--it's apparently called "Informed Delivery Interactive Campaigns". They use the example of a mailer advertising an online sale: recipients with Informed Delivery can click on the link right from the USPS dashboard to the sale website. They have a bunch of analytics you can get and the whole thing looks pretty sophisticated.
As far as I can tell, this is all free to mailers, at least for the moment. Maybe they're planning on charging for it later.
As far as I can tell, this is all free to mailers, at least for the moment. Maybe they're planning on charging for it later.
USPS docs here: https://www.usps.com/business/informed-delivery.htm