[zerocrates]

They don't seem to have fixed it. From their FAQ:

Is Informed Delivery® available to PO Box® customers?

USPS® is looking to expand the service to PO Box customers in the future. PO Box customers in certain Post Offices nationwide can use our existing Real Mail Notification® service to receive a text-only message without images, via email or SMS message. Check with your local Post Office for more details.

[Holmes]

Good to know. Thanks.