They are correct. The USPS has a universal service obligation. If you send a letter or parcel to any address in the US, the post office must deliver it.
I respectfully disagree. The postal service is held to a standard of service by a USO - Universal Service Obligation. [0]
This means it is an org mandated to accept your request for service at a reasonable price regardless of your location of residence. There is an important distinction between that, and being mandated to receive mail service. That is not a stipulation of being alive in USA.
This means it is an org mandated to accept your request for service at a reasonable price regardless of your location of residence. There is an important distinction between that, and being mandated to receive mail service. That is not a stipulation of being alive in USA.
[0] - https://www.uspsoig.gov/blog/postal-service-and-its-obligati...