We often hear the term Mail.dat in the mailing industry, but what exactly is it, and why is it important?

Mail.dat is an industry standard database file set that consists of detailed presort mailing information based on specifications set by the International Digital Enterprise Alliance (IDEAlliance) (http://www.idealliance.org/maildat/). Mail.dat is a group of files that together represent virtually all the detailed information regarding a mailing with the exception of the names and addresses of the recipients. It is created during the presort process by the presort software or MLOCR (multiple line optical character reader) machines and consists of data elements in a readily usable format. Mail.dat is the primary format of data files that is accepted by the U.S. Postal Service for exchanging electronic mailing information. In order to use Mail.dat, you need to apply for a User License Code from IDEAlliance, which involves payment of a nominal fee. Currently, there are hundreds of licensed Mail.dat users including mailers, software vendors, service providers, publishers, systems integrators, and the USPS.

The screen shot below shows a typical Mail.dat file set as viewed in Windows File Explorer.

Listing of Unzipped Mail.dat file sets. Each set or Mail.dat files can contain up to 21 files. Each Mail.dat set represents one mailing.

When the ZIP file 0012811.zip (shown in above screen shot) is expanded, it contains the files 0012811.XXX with XXX being hdr, seg, mpu, mcr, mpa, cpt, csm, cqt, pqt, pdr. These cryptic file extensions represent the type of file:

· HDR is the Header file, which contains basic information about the mailing.

· SEG is the Segment file, which describes the different segments of a mailing job, such as different versions of the mail piece.

· MPU is the Mail Piece Unit file, which describes the mail piece itself.

· MCR is the Mail Piece Unit/Component Relationship file, which describes the relationship of the various mail piece components in relation to the mail piece units.

· MPA is the Mailer Postage Accounting file, which describes how the postage is paid, permit numbers, etc.

· CPT is the Component file, which describes each component that makes up the mail piece, e.g. statement, insert, envelope.

· CSM is the Container Summary file, which details each container (e.g. sack, tray, pallet) of mail generated during the presort process.

· CQT is the Container Quantity file, which details the piece counts within each container of mail.

· PQT is the Package Quantity file, which details the piece counts within each package or bundle of mail pieces.

· PDR is the Piece Detail Record file, which includes specific identification data for each piece in the mailing. Mail.dat files must contain either a PDR file or a PBC file, which is the Piece Barcode file. The PBC files includes the Intelligent Mail barcode data for each mail piece.

There are additional extension names that could be included if that mailing needed them. There are currently 10 files required for each Mail.dat file set, with up to 21 files available if needed. The Mail.dat sets only contain those files that are needed to describe the mailing. For a full description of all the files, consult the IDEAlliance Mail.dat specification at https://www.idealliance.org/mail-dat.

Mail.dat provides you and your mailing partners with all the information needed to automate postal statement preparation, enhance transportation planning, speed mail acceptance and verification, and manage postage data. Using Mail.dat to create and exchange electronic documents with the USPS enables mailers to profit significantly from streamlining production and optimizing postage discounts such as drop shipping.

Mail.dat files also facilitate making changes to the original mailing plan as defined during the presort process. The presort process is often performed days or even weeks prior to the actual mailing date. That original presort plan can change during that time frame. Post-presort software allows mail preparers to make edits to the Mail.dat files to reflect those changes. For example, the weight of the mail pieces is estimated at the time of presort, and that data must the changed to the actual weight of the pieces once they are prepared. Another common example is splitting up a mailing job into smaller, more manageable portions. This may be done for production reasons, or perhaps to stagger the mailing job across multiple days to accommodate better control over the in-home delivery date. Regardless of the reason, these “partial” mailings can be identified and submitted to PostalOne! to accurately reflect what is physically mailed each day. These are just two examples; there are many edits and additional processes that can be performed using the Mail.dat file and post-presort software.

Mail.dat facilitates communication among all parties involved in a mailing

Because Mail.dat files are standardized, mail owners, list processors, lettershops, and transportation companies can – with the right Mail.dat software to read and manage these files – easily decode and transmit the mail production and postage information that the files contain. When Mail.dat files are available, all parties involved in a mailing can prepare in advance and allocate the proper resources for each job. Mail.dat becomes the bridge that not only links a variety of in-house lettershop/mail service provider applications, but also links the lettershop to its clients and of course to the USPS.

Jeff Peoples is CEO, Window Book.

This article originally appeared in the March/April, 2020 issue of Mailing Systems Technology.