How do you receive 0.55 rate on a First-Class letter within MailStream Plus

Product affected: MailStream Plus™, all versions, all platforms
This is in regard to the current 2019 First-Class 1 oz or less retail letter mail rate.  

MailStream Plus is for Commercial mailings, not Retail mailings.  Per the USPS rate tables, for commercial mailers the .55 rate isn't available because of discounts that are applied and given to commercial mail.
The .55 rate is available for First-Class letters if mailing as a retailer (meaning placing a personal 55 cent stamp on a letter).

Please see the USPS Pricing Chart url: for more pricing information.
UPDATED:  July 5, 2019