39 CFR Part 121

5 sections.

§ 121.0
§ 121.0 Market-dominant product service standards.
§ 121.1
§ 121.1 First-Class Mail.
§ 121.2
§ 121.2 Periodicals.
§ 121.3
§ 121.3 USPS Marketing Mail.
§ 121.4
§ 121.4 Package Services.

This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.