s-o-1036 June 1994

4.2.1. Names and Contents

Despite  the  restrictions  on header-name syntax imposed by
the grammar, relayers and  reading  agents  SHOULD  tolerate
header  names containing any ASCII printable character other
than colon (":", ASCII 58).

     NOTE: MAIL header  names  can  contain  any  ASCII
     printable  character (other than colon) in theory,
     but in practice, arbitrary header names are  known
     to  cause trouble for some news software.  Section
     4.1's restriction to alphanumeric sequences  sepa-
     rated by hyphens is believed to permit all widely-
     used header names without causing problems for any
     widely-used  software.   Software  is nevertheless
     encouraged to cope correctly with the  full  range
     of  possibilities,  since aberrations are known to
     occur.

Relayers MUST disregard headers not described in this  Draft
(that  is,  with  header names not mentioned in this Draft),
and pass them on unaltered.

Posters wishing to convey non-standard information in  head-
ers  SHOULD  use header names beginning with "X-".  No stan-
dard header name will ever be of this form.  Reading  agents
SHOULD  ignore  "X-"  headers,  or  at least treat them with

INTERNET DRAFT to be        NEWS                  sec. 4.2.1


great care.

The order of headers in an article is not significant.  How-
ever, posting agents are encouraged to put mandatory headers
(see section 5) first, followed  by  optional  headers  (see
section 6), followed by headers not defined in this Draft.

     NOTE:  While  relayers  and reading agents must be
     prepared to handle any order, having the  signifi-
     cant  headers (the precise definition of "signifi-
     cant" depends on  context)  first  can  noticeably
     improve  efficiency,  especially in memory-limited
     environments where it is difficult to buffer up an
     arbitrary  quantity of headers while searching for
     the few that matter.

Header names are case-insensitive.   There  is  a  preferred
case  convention,  which  posters  and posting agents SHOULD
use: each hyphen-separated "word" has its initial letter (if
any)  in  uppercase  and  the rest in lowercase, except that
some abbreviations have all letters  uppercase  (e.g.  "Mes-
sage-ID"  and "MIME-Version").  The forms used in this Draft
are the preferred forms for the  headers  described  herein.
Relayers  and  reading agents are warned that articles might
not obey this convention.

     NOTE: Although software must be prepared  for  the
     possibility  of random use of case in header names
     (and other case-independent text), establishing  a
     preferred  convention reduces pointless diversity,
     and may permit optimized software that  looks  for
     the  preferred  forms  before  resorting  to less-
     efficient case-insensitive searches.

In general, a header can consist of several lines, with each
continuation line beginning with white space.  The EOLs pre-
ceding continuation lines are ignored when processing such a
header, effectively combining the start-line and the contin-
uations into a single logical line.  The logical line,  less
the  header  name,  colon, and any white space following the
colon, is the "header content".