POSTNET is unlike other barcodes because data is encoded in the height of the bars instead of in the widths of the bars and spaces. Most standard barcode readers cannot decode POSTNET. This symbology was chosen by the Postal Service mainly because it is extremely easy to print on almost any type of printer. POSTNET is a fixed dimension symbology meaning that the height, width and spacing of all bars must fit within exact tolerances.
Microsoft Access and Word have built in tools for generating PostNet barcodes. See our tutorial on how to use the tools in word to created PostNet barcodes in your mail merge documents.
FIM or Facing Identification Mark patterns are another type of postal barcode used in automated mail processing by the U.S. Postal Service. FIM patterns are used for automatic facing and canceling of mail that does not contain a stamp or meter imprint (business reply mail, penalty mail, etc.). They also provide a means of separating business and courtesy reply mail from other letters. Three FIM patterns are currently in use. FIM-A is used on courtesy reply mail that has been preprinted with PostNET barcodes. FIM-B is used on business reply, penalty and franked (government) mail that is not preprinted with PostNET barcodes. FIM-C is used on business reply, penalty and franked mail that has been preprinted with PostNET barcodes. FIM patterns are placed in the upper right corner along the top edge and two inches in from the right edge of letters and cards. For more information about all postal barcodes contact your local post office.