> ....the Postal Service is working on an approach that it hopes to make available to the public in January 2018 which would allow USPS to send written notification to addresses when someone at that residence signs up for Informed Delivery.

Written notification is good. In addition they should implement mail-based authorization, where an activation code is mailed to the customer, and the code must be entered on the Informed Delivery web site to confirm participation in the program.