What does an email header reveal about the email transmission?

The transmission of an email can be traced through the information contained in the email header, which provides critical details about the path the email has taken from the sender to the recipient. The header includes various fields such as "From," "To," "Subject," and, most importantly, technical information like the "Received" fields that show the servers through which the email passed, including timestamps for each hop.

This route information is essential in forensic investigations as it can be used to establish timelines, identify the source of the email, and even the integrity of its transmission. It can also assist in tracking down spam or malicious emails by revealing the path taken by those messages.

While the other choices address aspects that may not be directly included in the header, such as emotional tone, priority level, or the exact device used to send the email, they do not provide the same level of detail regarding the transmission journey itself. Therefore, the correct answer accurately captures the primary and most relevant function of an email header in revealing the route the email has taken.