Why A formal radiogram has several distinct parts: preamble, address, text, and signature. The preamble is the bookkeeping header, containing the message number, precedence, handling instructions, station of origin, check (word count), place of origin, and time and date filed. All of that exists so any station in the relay chain can identify, verify, and trace the message back to its source.
Watch out The recipient's street address, phone number, or email belong in the address block of the radiogram, not the preamble; the preamble never carries delivery information.
Preamble = paperwork. Number, precedence, station of origin, check, date: everything needed to trace, nothing about the recipient.