Mail.XML vs Mail.Dat The Present and Future Tools By Monica Lundquist, Postal Affairs WindowBook

                           Mail.XML vs. Mail.dat

Most of us in the mailing industry have become accustomed to the word “mail.dat” and have a good understanding of what it is and the benefits of using it. For those of you still not familiar with the term mail.dat, it is a mailing industry standard specification (established and maintained by IDEAlliance) for a set of relational database files. These files are generated at the time that the mailing list is sorted through postal presort software, or when the mailpieces are sorted on Multi-Line Optical Character Reader (MLOCR) sorters. The set of files together represent just about all the specifics about a mailing with the exception of the mailing names and addresses. These files are used by the mailing industry and the United States Postal Service® (USPS) to share information and facilitate electronic transactions.

Just when we thought we had become pretty smart about mail.dat, along comes Mail.XML. Unless you are a real techie, mail.xml probably seems like a word from a foreign language. Actually, mail.xml is fairly simple, and it represents a really cool method to transmit mailing information. But what does it mean for the average mailer?

As background, Mail.XML is a newer mailing industry standard specification (again established and maintained by IDEAlliance) for informational transmissions. Mail.dat is quite robust and can contain huge amounts of information. This is very beneficial, except when you only need portions of the information that resides in mail.dat files. In these cases, it can be time consuming and a strain on transmission and storage resources to send entire Mail.dat files back and forth between the involved participants in the mailings.

To help understand the difference between Mail.dat and Mail.XML, think of it in terms of the Mail.dat file being the encyclopedia of a Mail.XML given mailing. Then think of Mail.XML being the telegram that you send to someone describing a portion of the encyclopedia. If your recipient only needs a small segment of information, it is much easier (for both of you!) to send them a short telegram than to send them an entire encyclopedia. That is essentially how Mail.XML works in relationship to mail.dat.

One of the ways that Mail.XML will be used is during transactions with the USPS. For example, if you use PostalOne! to transact business with the USPS, you will first upload a mail.dat file for the mailing as a “planned” mailing. Once all the final attributes of the mailing have been determined and all adjustments made to the Mail.dat file, you need transmit only Mail.XML “telegrams” to the USPS to update the mail.dat file that you previously uploaded. This eliminates the need to re-upload an entire mail.dat file every time a change is made or a new transaction required. This allows you to pay postage, make drop ship appointments, and a variety of other transactions using much smaller chunks of data.

Mail.dat is not going away anytime soon, and will certainly not be replaced by mail.xml. Mail.XML is just a very useful tool for use in transmitting smaller chunks of a mail.dat file. You’ll be hearing lots more about Mail.XML, particularly as the USPS proceeds with the integration of Intelligent Mail®.

Monica Lundquist, Postal Affairs, Window Book, Inc.

Mail.XML A Present and Future Tool

Mail.XML is a mailing industry standard specification for light-weight transactions between participants in the mailing process. The Mail.XML specification, as with the mail.dat specification, was established and is maintained by IDEAlliance.

Mail.dat is the powerful foundation for communicating data regarding mailings. It is a suite of relational database files which contain virtually every piece of data about a mailing except for the actual name and address records.

Mail.XML is a communications tool which allows for participants in the mailing process to communicate changes and updates to the Mail.dat file in a fast, efficient manner which is almost real-time. There are numerous transactions that occur during the course of the mailing process which do not require transmission of the entire Mail.dat database. Using Mail.XML for these lighter-weight transactions reduces manual data entry processes and makes these transactions quicker and more efficient.

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 between mail owner, list house, manufacturer/printer, logistics company and the USPS.


The United States Postal Service® (USPS) continues to move toward a forms-based transaction protocol, to which Mail.XML lends itself beautifully. For example, transmitting postage statements to the USPS for postage payment is a forms-based transaction, for which Mail.XML may be used. Making drop ship appointments through the USPS FAST system is another example.

Mail.dat is not going away and will not be replaced with Mail.XML. Rather, Mail.XML is a powerful tool to make mailing transaction communications much quicker and easier. Window Book offers numerous world-class Mail.XML solutions for communications between mail owners, mail preparers, the USPS and other suppliers. Come join us and tap into the future today!