Publication 417, Nonprofit USPS Marketing Mail Eligibility: Nonprofit and Other Qualified Organizations > 1 Introduction > 1-3 Mailing Standards
Mailing Standards of the United States Postal Service, Domestic Mail Manual (DMM) provides the official mailing standards and prices for all domestic mail services.
The DMM is available for customers and employees on Postal Explorer at pe.usps.com. The online version includes easy-to-use interactive menus, clickable links, and a powerful search feature.
Customer Support Rulings (CSRs) provide examples of DMM standards and how they are applied to actual mailing situations. CSRs are available at pe.usps.com and are easy to search or sort (by class of mail, DMM reference, etc.).