Intelligent Mail Matrix Barcode (IMmb) Technical Specifications

Shipping labels on irregularly-shaped packages, softpacks, and polybags can easily become distorted or creased during automated parcel processing making reading the traditional, linear IMpb barcode challenging to scan.  USPS has developed the IMmb to help overcome these challenges and improve package visibility.  IMmb barcodes contain the same data as is in the IMpb barcode; however, they use a more robust, space-efficient robust barcode symbology for encodation.  The smaller barcode footprint allows two IMmb barcodes to be added within unused areas of existing standard shipping labels.  The result is redundancy of the barcode data giving sorters two additional chances to read the barcode. 

The US Postal Service® requires  IMmb barcodes on all package shipping labels.

Z4 Info File

A downloadable ZIP file containing information related to the Z4 Info File

Early Warning System (EWS002C0.ZIP)

This file is the EWS production file and is updated weekly. This file contains the Early Warning System data file for the CASS™ and MASS™ certification process.

PTR2 Release Notes_DD_03_03_26

INFORMATIONAL - Delayed Receipt of Data Daylight Savings Time Issue – March 08, 2026

Manifest Mailing System Exception Request Form

Effective April 1, 2026 - The Postal Service is retiring Publication 401 Manifest Mailing System (MMS) used for mail sortation and preparation with hard copy forms and documentation. Affected customers must migrate to Electronic Documentation (eDoc), Full Service, Seamless, and eInduction, for Letters, Cards, and Flats April 1st,, 2026.

Mailers who require a onetime exception to continue using the Manifest Mailing System—due to an inability to meet the deadline to migrate to Full Service, Seamless, or USPS Ship, may do so by submitting their request to their local Manager Business Mail Entry.

INFORMATIONAL - Upcoming Maintenance Change Request - CHG1235463

INFORMATIONAL - USPS Ship Data Feed Update - New Notifications for Duplicate & Unmanifested Packages

March 8 2026 Release Notes

Ancillary Service Endorsement Fact Sheet

Ancillary service endorsements are used by mailers to request an addressee’s new address or the reason mail cannot be
delivered as addressed and to provide the US Postal Service with instructions on how to handle Undeliverable As Addressed
(UAA) mailpieces.

DELIVERY - Military Post Offices Temporarily Suspended Updated

DELIVERY - International Service Suspension Notice

Brewed for Business: The Shipping Mini Café

INFORMATIONAL - New Premium Forwarding Service Commercial - Coming Soon

INFORMATIONAL - PME Embargo Due To Chemical Spill Memphis, TN FedEx Hub

PCC Events (March 2026)

February 2026 Nixie Volume

This spreadsheet contains the UAA statistics for February 2026.

INFORMATIONAL - Federal Register - Manifest Mailing System Retiring

INFORMATIONAL - NCOA API Launching July 2026

PTR2 Release Notes_DD_02_28_26

Informed Visibility Mail Tracking & Reporting Machine Count

List of US Postal Service machines by site, including a description of each machine.

ZIP Codes by Area and District codes

The Excel spreadsheet lists ZIP Codes with the associated Area and District Codes.  

***Updated - New Areas*** - Area District 5-digit ZIP Codes (AREADIST_ZIP5.TXT)

USPS Ship Data Dictionary

Detailed information on the USPS Ship (Formerly Package Platform) data elements available through the Informed Visibility Mail Tracking & Reporting (IV-MTR) application. Please note that items in bold text were updated or added recently.

Automated Zone Indicator (AZI) Table

The AZI table lists each five-digit ZIP Code™ and is an indicator of the type of processing that typically takes place on letter mail destined for each ZIP Code. Each number in the file is a ZIP Code appended with a numeric zone indicator. The five numeric indicators are as follows:

1. Two Pass Zones: Automated two-step sector/segment at mail processing facilities
2. 876 Carrier Route Sort Zones: Automated incoming secondary carrier route sorting at plants
3. Carrier Route Barcode Sorter (CSBCS) Zones: Automated walk sequence sorting on CSBCS machines at delivery units
4. Delivery Barcode Sorter (DBCS) Zones: Automated walk sequence sorting on DBCS machines at plants [i.e., sectional center facilities (SCFs)] or at delivery units
5. Manual/Mechanized Zones: No automated sorting; no tracking code scans should be generated from facilities matched to these ZIP Codes