Publication 52 - Hazardous, Restricted, and Perishable Mail > Appendix C > USPS Packaging Instruction 2D
Foodstuffs and soap products that are held in containers under pressure are mailable in the domestic mail via surface transportation if they qualify as a Limited Quantity surface material and all applicable requirements in 342 are met.
The following labels and text markings must be placed on the address side of the mailpiece unless specified in 221.1 and 325.1.