Which information is included in an email header?

Comprehensive and Detailed Explanation From Exact Extract:

An email header contains metadata about the email including sender, receiver, routing information, and content details. TheContent-Typeheader specifies the media type of the email body (e.g., text/plain, text/html, multipart/mixed), indicating how the email content should be interpreted.

Sender's MAC address is not typically included in email headers.

Number of pages is not relevant to email metadata.

Message-Digest is a term related to cryptographic hashes but is not a standard email header field.