15.2 Mail Message Format
The mail message format is specified by the RFC 822 standard. Every email message contains a message header and a message body. The message header is separated from the message body by one blank line (CR LF CR LF). The header and the body of the message use only ASCII characters.
The header is formed from individual header fields. Every header field begins with a keyword followed by a colon. Parameters can be listed after the keyword. The header field ends at the end of a line (i.e., CR LF).
Spaces and tabs may be inserted between individual parts of the header field. The header field may continue on the next line. However, in such a case, the next line must begin with a space or tab (the keyword of the header field must ...