ARRL Radiogram
An ARRL radiogram is an instance of formal written message traffic routed by a network of amateur radio operators through traffic nets, called the National Traffic System (NTS).
It is a plaintext message, along with relevant metadata (headers), that is placed into a traffic net by an amateur radio operator. Each radiogram is relayed, possibly through one or more other amateur radio operators, to a radio operator who volunteers to deliver the radiogram content to its destination.
Within the United States, amateur radio operators can send and deliver radiograms on behalf of any member of the general public; this is one type of "third-party traffic" that is specifically permitted by Federal Communications Commission (FCC) rules.