The Intelligent Mail barcode (formerly known as the 4-State Customer Barcode) is the next generation of USPS® barcode technology used to sort and track letters and flats with unprecedented accuracy and ease. 

The suite of Intelligent Mail barcodes contains three separate barcodes. The Intelligent Mail barcode is applied to individual mailpieces (letters, cards and flats). The Intelligent Mail Tray barcode is applied on tray labels that are attached to trays, sacks, and tubs, and the Intelligent Mail Container barcode is applied on container labels (or placards) that are attached to handling units such as pallets, containers, and APCs.

The suite of barcodes for Intelligent Mail share some common characteristics: identify the owner or sender of the mailpiece, identify the mailpiece or mail aggregate to allow for tracking, encode product or service requests on individual mailpieces or to include unique indicators for processing mail aggregates, and provide sorting and/or routing information.