Here are updated links for Intelligent Mail Package Barcode:
Updated List: Service Type Codes for Intelligent Mail® Package Barcode (IMpb)
This document provides the updated service type codes for Intelligent Mail® Package Barcodes.
IMpb/IMmb Electronic File Transmission Requirements
Intelligent Mail® Package Barcode (IMpb) Specification
This document provides specifications for generating and printing the US Postal Service (USPS) Intelligent Mail® Package Barcode (IM™ Package Barcode). Additionally, this specification governs the production of “Extra Service” barcodes such as Certified, Insurance, Delivery Confirmation, Signature Confirmation, etc.