Intelligent Barcodes Needed for Automation Pricing:
Beginning May 2011, to be eligible for automation prices on letter-size and flat-size mail pieces, mailers will need to use the IMb, either the Full Service or Basic option, in place of the POSTNET barcode.
To learn more, click on this USPS link: http://www.usps.com/mailpro/2010/sepoct/page6.htm