Appendix VI:  Limited MIME Support

     This  version  of  INN  includes  limited  support  for  MIME,  the
Multipurpose  Internet  Mail  Extensions,  described  in  RFC 1341.  The
support is the  ability  to  do  limited  transport  of  arbitrary  MIME
messages,  and  nnrpd can add MIME headers to all local postings that do
not have them.

     In addition, there are patches available for nntplink that allow it
to  do  MIME  transport.  The patches are not (yet) part of the official
release;   if   you   need   them,    contact    Christophe    Wolfhugel
<Christophe.Wolfhugel@hsc-sec.fr>; he did most of the INN work, too.

     You should be very careful if you have nnrpd add MIME headers.   To
do  this,  edit  inn.conf  as indicated in doc/inn.conf.5.  Once this is
done, all articles posted will get MIME headers  added.   Existing  MIME
headers  will  not  be  modified,  but  missing ones will be added.  The
default values to add to inn.conf are these:

     mime-version: 1.0
     mime-contenttype text/plain; charset=us-ascii
     mime-encoding: 7bit

An internationalized site might want to use these values:

     mime-version: 1.0
     mime-contenttype: text/plain; charset=iso-8859-1
     mime-encoding: 8bit

It is possible to use these values because INN provides a  clean  eight-
bit  data  path.   Unless you make special arrangements with your peers,
however, you must transmit seven-bit  data.   Doing  this  will  require
special  transmit  agents.   Note  that  nnrpd  is not a Mime-compatible
reader.  You must have software to  extract  the  data  and  present  it
appropriately.

     If you configure your site to use seven-bit  data,  then  you  must
also  make  sure  that none of your software creates eight-bit articles.
Nnrpd does not verify this.  If you configure your site to use eight-bit
data,  then ASCII works fine, but remember that in quoted-printable long
lines are cut and that the equal sign ("=") is quoted; this is  really
bad for source code postings, among others.

     The character set can also cause problems.  If you use  "iso-8859-
1"  you  must  make sure that your posting software uses this character
set (e.g., not CP-437 under  MS-DOS)  because  nnrpd  does  not  do  any
conversion.

     In general, be very cautious.

     MIME articles can only be sent using innxmit; work on batcher is in
progress.  Unless the "-M" flag is used, no MIME conversions are done.
If the flag is used, the following happens:  Articles  with  a  Content-
Transfer-Encoding  header  of  "8bit"  or  "binary"  are forwaded in
"quoted-printable" format (the "base64"  format  will  be  available
soon).  All other articles -- in particular, those without MIME headers,
those of type "message" or "multipart," those with Content-Transfer-
Encoding header of "7bit" -- are forwarded without any change.