Which part of the email header logs the history of a message, including origin and forgery details?

The correct choice highlights the significance of the "Received" field in the email header as it provides a chronological log of the servers that the email passed through during its journey from sender to recipient. Each mail server that handles the email adds its own "Received" entry, which includes timestamps, sender and recipient IP addresses, and the server's identifying information. This information is crucial for tracing the path of an email and is particularly useful during investigations of email forgery or spam. By analyzing these entries, incident handlers can identify any anomalies or attempts to spoof sender information, thus gathering evidence about the email's origin.

While the other fields in an email header serve specific purposes, they do not provide the same detailed tracking and historical logging capabilities as the "Received" field. For instance, "X-Mailer" identifies the software used to generate the email, "Subject" gives a brief topic of the message, and "Message-Id" serves as a unique identifier for the email itself. However, none of these contain the sequential routing history or detailed information essential for understanding potential forgery issues.