gnus: Crosspost Handling

 
 3.29 Crosspost Handling
 =======================
 
 Marking cross-posted articles as read ensures that you’ll never have to
 read the same article more than once.  Unless, of course, somebody has
 posted it to several groups separately.  Posting the same article to
 several groups (not cross-posting) is called “spamming”, and you are by
 law required to send nasty-grams to anyone who perpetrates such a
 heinous crime.
 
    Remember: Cross-posting is kinda ok, but posting the same article
 separately to several groups is not.  Massive cross-posting (aka.
 “velveeta”) is to be avoided at all costs, and you can even use the
 ‘gnus-summary-mail-crosspost-complaint’ command to complain about
 excessive crossposting (SeeSummary Mail Commands).
 
    One thing that may cause Gnus to not do the cross-posting thing
 correctly is if you use an NNTP server that supports XOVER (which is
 very nice, because it speeds things up considerably) which does not
 include the ‘Xref’ header in its NOV lines.  This is Evil, but all too
 common, alas, alack.  Gnus tries to Do The Right Thing even with XOVER
 by registering the ‘Xref’ lines of all articles you actually read, but
 if you kill the articles, or just mark them as read without reading
 them, Gnus will not get a chance to snoop the ‘Xref’ lines out of these
 articles, and will be unable to use the cross reference mechanism.
 
    To check whether your NNTP server includes the ‘Xref’ header in its
 overview files, try ‘telnet your.nntp.server nntp’, ‘MODE READER’ on
 ‘inn’ servers, and then say ‘LIST overview.fmt’.  This may not work, but
 if it does, and the last line you get does not read ‘Xref:full’, then
 you should shout and whine at your news admin until she includes the
 ‘Xref’ header in the overview files.
 
    If you want Gnus to get the ‘Xref’s right all the time, you have to
 set ‘nntp-nov-is-evil’ to ‘t’, which slows things down considerably.
 Also SeeSlow/Expensive Connection.
 
    C’est la vie.
 
    For an alternative approach, SeeDuplicate Suppression.