Here is the reality you face. The USPS is a federal government entity, not a private business. This has several implications for you. First, you must sue the federal government in federal court. As a result, there is no option to go to state small claims court for this. Second, in order to sue a federal agency for money damages, you must point to a federal statute that waives the government's sovereign immunity for the type of claim you wish to bring. Negligence claims are tort claims. When it comes to tort claims the Federal Tort Claims Act (FTCA) provides the waiver needed for most tort actions. But unfortunately for you, the statute expressly excludes claims for negligent delivery of the mail from the FTCA. So you cannot successfully sue the USPS for negligence in handling the mail. It is also possible to sue the USPS for breach of contract, but you have the problem that the service is free, which makes meeting all the elements to prove a contract challenging. Even if you succeeded in doing that, you have no direct damages from the breach for which to sue. Consequential damages are generally not awarded in contract actions. Finally, even if you might have been able to win a few bucks, your costs to do it would far outweigh what you get, making it financially not worthwhile to pursue.