rfc2822 April 2001

3.5 Overall message syntax

   A message consists of header fields, optionally followed by a message
   body.  Lines in a message MUST be a maximum of 998 characters
   excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
   characters excluding the CRLF.  (See section 2.1.1 for explanation.)
   In a message body, though all of the characters listed in the text
   rule MAY be used, the use of US-ASCII control characters (values 1
   through 8, 11, 12, and 14 through 31) is discouraged since their
   interpretation by receivers for display is not guaranteed.
message         =       (fields / obs-fields)
              [CRLF body]

body            =       *(*998text CRLF) *998text

   The header fields carry most of the semantic information and are
   defined in section 3.6.  The body is simply a series of lines of text
   which are uninterpreted for the purposes of this standard.