usefor-article-03 February 2000

6.17.3.  Content-Type

   The Content-Type: "text/plain" is the default type for any news
   article, but the recommendations and limits on line lengths set out
   in section 4.5 SHOULD be observed. The acceptability of other
   subtypes of Content-Type: "text" (such as "text/html") is a matter of
   policy (see 1.1), and posters SHOULD NOT use them unless established
   policy or custom in the particular hierarchies or groups involved so
   allows. Moreover, even in those cases, the material SHOULD, for the
   benefit of readers who see it only in its transmitted form, be
   "pretty-printed" so as to keep it within the line lengths recommended
   in section 4.5, and to keep any sequences which control its layout or
   style separate from the meaningful text.
   In the same way, Content-Types requiring special processing for their
   display, such as "application", "image", "audio", "video" and
   "multipart/related" are discouraged except in groups specifically
   intended (by policy or custom) to include them. Exceptionally, those
   application types defined in [RFC 1847] and [RFC 2015] for use within
   "multipart/signed" articles, and the type "application/pgp-keys" (or
   other similar types containing digital certificates) may be used
   freely but, contrary to [RFC 2015] and unless the article is intended
   to be sent by mail also, the Content-Transfer-Encoding SHOULD be left
   as "8bit" (or "7bit" as appropriate).

   Reading agents SHOULD NOT, unless explicitly configured otherwise,
   act automatically on Application types which could change the state
   of that agent (e.g. by writing or modifying files), except in the
   case of those prescribed for use in control messages (7.1.2 and
  ).