USPS provides the clearest official purchase route. Amazon and eBay contain seller-specific listings, so safety must be judged by the individual seller, fulfillment, return terms and exact product.
Do not rank platforms as a single seller
A marketplace listing proves only that an item is offered. Review seller history, product identity, condition, price, shipping and return protection for that listing.
Understand approved-provider claims
USPS Approved Postal Provider status is limited to providers operating under applicable USPS arrangements. An independent shop cannot call itself certified or approved without a verifiable official record.
Treat extreme discounts as a warning
Compare the delivered price with postal face value and equivalent offers. An implausibly low price increases risk but does not by itself prove counterfeit postage.
No guaranteed visual test
UV light, microprinting, texture or packaging cannot provide a universal authenticity guarantee from a photo. Prefer traceable sellers, retain records and report suspected counterfeit postage through USPIS.
Sources and update note
Issue facts and current postal rules should be checked against the linked primary sources. Prices, inventory, services and policies can change.