Publication 52 - Hazardous, Restricted, and Perishable Mail > Appendix C > USPS Packaging Instruction 4B
Safety matches (book, card, or strike–on–box) may be mailed only in domestic mail via surface transportation, provided all applicable requirements in 344 are met, including:
Note: Strike–anywhere matches assigned UN1331 and other types of matches assigned UN2254 or UN1945 are nonmailable.