VERIFIED SOLUTION i
Looking in the MailStream Plus (MSP) 8.2.1 Reference guide, at the ML TYP parameter, in position 14, these are the defaults for Standard Flats (when not palletizing)–
1 Periodicals and Standard Mail, without carrier
2 Periodicals and Standard Mail, with carrier
Which are -
1 705.9 Co-trayed/Sacked Flats
2 705.10 Merged Flats
Several years ago the USPS came up with the optional merged presort groups for Flats mailings that allows mailers to presort (merge) together Automation and Nonautomation pieces in the same bundles. But if you want to turn this off, you can change this to N (No special presort) to separate the presort groups.
Be aware this will may increase the cost of your mailing.
For example, if you have 9 pieces to ZIP Code 12345 that have a ZIP/ZIP+4 and Delivery Point Code (DPC), and 6 records to the same ZIP Code that are missing the ZIP+4 and DPC.
Using the ML TYP with position 14 blank, the 9 pieces will get the 5-digit automation rate and the 6 records will get the 5-digit Nonautomation rate of the sack destination.
If you turn off the Merged presort logic (N in position 14 of the ML TYP), these pieces will fall down to a higher cost bundle, like a 3-digit until there are enough pieces to make a bundle in their separate presort groups.
UPDATED: August 7, 2017