An email message must contain certain pieces of information,
called headers, which specify the message's sender,
recipient(s), and so on. At the top of the mail buffer is a set
of header fields, where you can enter this information. You can
insert and edit header fields using ordinary editing commands.
See Header Editing, for commands specific to editing header
fields. Some header fields are automatically pre-initialized in
the buffer, when appropriate; other headers, such as ‘Date’ and
‘Message-Id’, are normally omitted from the mail buffer and
created automatically when the message is sent. The line in the
buffer that says --text follows this line-- separates the header
fields from the body (or text) of the message. Everything above
this 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. The text used for the
delimiter line is controlled by the variable Here is an example
of what the headers and text in