Here is an example of the contents of a mail buffer:
To: firstname.lastname@example.org CC: email@example.com, firstname.lastname@example.org Subject: Re: What is best in life? From: email@example.com --text follows this line-- To crush your enemies, see them driven before you, and to hear the lamentation of their women.
At the top of the mail buffer is a set of header fields, which are used for specifying information about the email's recipient(s), subject, and so on. The above buffer contains header fields for ‘To’, ‘Cc’, ‘Subject’, and ‘From’. Some header fields are automatically pre-initialized in the mail buffer, when appropriate.
The line that says ‘--text follows this line--’ separates the header fields from the body (or text) of the message. Everything above that line is treated as part of the headers; everything below it is treated as the body. The delimiter line itself does not appear in the message actually sent.
You can insert and edit header fields using ordinary editing commands. See Header Editing, for commands specific to editing header fields. Certain headers, such as ‘Date’ and ‘Message-Id’, are normally omitted from the mail buffer and are created automatically when the message is sent.