Pricing & Classification DMM Advisory

Message board to keep postal customers informed of changes to mailing standards, services, and prices.

April 2, 2010

PostalOne! New Mail.dat Client

On November 15, 2009 the Postal Service™ introduced a new USPS® Mail.dat client to upload Mail.dat 8-2 files which replaced the legacy Mail.dat client application. Mailers submitting new Mail.dat, version 8-2 jobs must download and utilize the new USPS Mail.dat client software. Go to section 3.0 of the Postal Service Mail.dat Technical Specification (version 8.8) for release 24 for information on the USPS Mail.dat client software.

In the PostalOne!® Release 24.0 deployed on March 14th, 2010, the Postal Service discontinued the support of the legacy Mail.dat client software. Since then some mailers have requested a temporary extension to complete jobs via the legacy client software that were submitted prior to March 15th. In order to allow mailers time to complete their jobs without resubmitting, we made a one-time exception to temporarily activate the legacy Mail.dat client software until April 16, 2010.

Mailers may not submit any new jobs using the legacy Mail.dat client software. This support will be permanently discontinued on April 16th, 2010. The PostalOne! help desk is available via email at or by calling 1-800-522-9085.