This summary is not the rule. The rule text controls.
When someone files a petition to adopt a child through the Hague Convention process, they have to send a copy of that petition to certain people and offices. This includes all the extra documents, or exhibits, that go along with the petition.
The papers must go to the state department that handles adoptions, as well as any agency that has legal custody of the child. The sender has to mail these documents using registered or certified mail, and ask for a return receipt so there's proof the mail was delivered. Postage has to be paid ahead of time, and the address on the envelope needs to be correct and complete.
This rule exists to make sure everyone involved in the adoption knows about the case and has a chance to respond. It also creates a paper trail showing that proper notice was given, which protects the adoption process from later legal challenges based on improper notification.