Information MailStream Plus where to find what Mail.dat files are required to be uploaded to PostalOne!

Any Mail.dat files that MailStream Plus (MSP) generates that have data in them should be uploaded to PostalOne!.  Empty files should not be uploaded.
On Windows and UNIX/Linux, empty files are automatically deleted when the MailStream Plus job ends.  Any files that remain will have data and should be uploaded.  
On other platforms such as Mainframe or IBMi, the user needs to determine which files have data and so should be uploaded.
Mail.dat files that are *always* required will be generated automatically when there is a REPORT MAILDAT parameter in the MailStream Plus (MSP) job.
Mail.dat files that are optional can be selected by settings on the REPORT MAILDAT parameter. 

Regarding what Mail.dat files need to be generated, that can vary with the mailing being done, and there are several categories:
-Some Mail.dat files are always required, and there is no option regarding creating them.  MailStream Plus always generates them and populates them.
-Some files are optional/required in that there may be two possible files allowed, and the mailer can select *which* to produce, but a selection of one of them is required.
-Some files are required when doing a certain type of mailing.  For example for a Walk-Sequence Carrier Route mailing it needs the WSR file, or for taking incentive discounts the CCR file is required.
-Some files are totally optional, and the mailer can select if they want them to be generated.
The Idealliance association, along with the USPS, control the Mail.dat Specifications for each version.  The specifications give information about which category above the files fall into for each Mail.dat version. The specifications and information are available here-

The USPS Mail.dat specification's can in some cases be different than those from Idealliance.  They can be found here-
Environment Details
UPDATED:  April 3, 2018