What does the MailStream Plus 'E CODE' parameter do?

Configuration: All versions of MailStream Plus
The E CODE parameter defines the location and length of the field for the Entry Point ID Code.  E CODE can be used in two ways:

If only ENT PT parameters are being used, the E CODE tells MSP where the entry point ID code is located in each of the records.  Then MailStream Plus (MSP) will look in that location in each record and match and assign the record to one of the ENT PT entry point parameters in the job.  If no match is found, then the record will be assigned to the default ENT PT (if there is one, with a Y in position 72.) 

If the job is using SCF PT and/or ADC PT and/or NDC PT to tell MSP to automatically determine and assign the records to entry points, then the E CODE tells MSP where to *post* the entry point code into the records.
UPDATED:  April 21, 2017