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Final Mail.dat specification was published on August 9th and can be found at


Summary of the changes


  • New Fields for Reply Rides Free, Saturation/High-Density Incentive programs from USPS.
  • Place to enter Delivery Statistics File Date.
  • As of release 26 Jan 2011the Postal Service will not support Priority Mail via Mail.dat.
  • Changes in processing and rate category from exigency plan – please see USPS Jan. 2, 2011 Proposed Price for more details on proposed exigency price changes
  • Fields to support FSS (please see FRN .
  • Support for Air-Freight boxes



Things to note regarding this spec and PostalOne!


  • Industry agreed on a Must Catch 30 day prior to exigency and a Must Send 30 days after exigency.
  • o Must Catch Date : 02-Dec-2010 and
  • o Must Send Date 02-Feb-2011
  • The USPS is looking into options, but as things currently stand, PostalOne! will be able to “Catch” a Mail.dat 11-1 on the day of exigency (02-Jan-2011).
  • Any changes approved afterthe PRC review will be handled through errata.
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