If you're not aware of QR codes, they essentially function like bar codes, but can send consumers to a website, be used to redeliver a package, or for myriad other uses. The USPS mobile app makes extensive use of QR codes.
We can use QR codes on our direct mail to also:
• Send consumer to a custom landing page with an offer.
• Trigger a phone call to your business.
• Redirect to a personalized web page, customized to the recipient.
The possibilities are many – get creative! https://faq.usps.com/s/article/What-is-USPS-Mobile