In original mode, which acknowledgment code is returned by the receiver if the originating message passes original syntactic validation but then is not processed successfully?

The acknowledgment code that is returned by the receiver when the originating message successfully passes original syntactic validation but fails to be processed successfully is indeed the application error code, represented as AE.

This code indicates that while the format and structure of the incoming message were correct, there was a problem during the processing stage, such as a business rule violation or a failure in an application-specific context that rendered the message unprocessable.

The distinction here is important because it highlights the difference between syntactic validation—which checks that the message conforms to defined structural rules—and semantic processing, which involves ensuring that the content of the message makes sense and adheres to specific application dynamics or rules.

Understanding this distinction helps clarify the functionality of these acknowledgment codes within the HL7 messaging framework, as it emphasizes the role of each code in conveying specific types of responses regarding the state of message processing.