The AS2 headers that are returned with the receipt.
ReceiptHeaders should include headers such as AS2-From, AS2-To, Date, Content-Type, etc.
In the Send Adapter, this property will be populated after the full receipt is received from the server, if synchronous MDN delivery was requested.
In the Receive Adapter, these will be added to the HTTP headers when returning a synchronous reply, or to the SMTP headers when returning an asynchronous reply via email. If any additional headers are supplied in ReceiptHeaders, they will be prepended to the headers generated by the adapter.