Understanding when MailStream Plus puts break marks on First-Class Automation postcards 'bundles' and the tray is full

Product Affected:  MailStream Plus™
POSTBK is the parameter to use to put break marks on mail pieces.  POSTBK allows you to post a user's-choice code in the Name-Address output records to indicate the records which are at the start and end of pallets, and/or the start and end of Trays/Sacks, and/or the start and end of bundles.

But for automation postcards in full trays, MailStream Plus™ (MSP) POSTBK does *not* apply break marks.  Although you have to 'bundle' postcards just so-as to keep them lined up and facing correctly, in full trays the USPS does not regulate specifically where the breaks have to be, so specific break marks are not indicated for those pieces.

POSTBK and all other parameters are defined along with their usage in the MailStream Plus™ Reference Guide
UPDATED:  March 19, 2019