Mail.XML vs Mail.Dat
Mail.dat stores complete information about a mailing as a database. Prior to Mail.XML, the complete dataset was interchanged between the list house, printer/manufacturer, trucking company and USPS.
Mail.dat will not be replaced by Mail.XML. Mail.XML provides an alternative to exchanging the entire Mail.dat database. Mail.XML adds a new light-weight transaction messaging mechanism betweeen mail owner, list house, manufacturer/printer, logistics company and the USPS.