Any window envelope used for letter-size or flat-size mail must meet the following additional standards:
Any window envelope used for letter-size or flat-size mail claimed at automation prices, or for letter-size mail claimed at Enhanced Carrier Route High-Density or Saturation letter prices, must meet the barcoding standards for letters. For all letter-size mail in window envelopes, every character in the delivery address, including any Intelligent Mail barcode, marking, or endorsement, must be completely visible through the window throughout the full range of movement of the insert bearing the delivery address.
