The app is called PaperKarma.

What you do is sign up with the PaperKarma app and provide your mailing info securely to PaperKarma.
Then from the app when ever you get junk mail, Take a picture of the junk mail in a way that shows identification of what company send the junk mail. PaperKarma then looks up whoever is sending you the junk mail and if its in their database they will send a request for you to stop the company from sending you any more junk mail.

You even get a notification after like 30 minute if they were successfully able to locate the company and stop them from sending you any more junk Mail.