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### 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 (see Summary 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 see Slow/Expensive Connection.

C'est la vie.

For an alternative approach, see Duplicate Suppression.