that fetching will probably be slower. If this variable is @code{nil},
@code{nntp} will never split requests. The default is 5.
+@item nntp-xref-number-is-evil
+@vindex nntp-xref-number-is-evil
+When Gnus refers to an article having the @code{Message-ID} that a user
+specifies or having the @code{Message-ID} of the parent article of the
+current one (@pxref{Finding the Parent}), Gnus sends a @code{HEAD}
+command to the @acronym{NNTP} server to know where it is, and the server
+returns the data containing the pairs of a group and an article number
+in the @code{Xref} header. Gnus normally uses the article number to
+refer to the article if the data shows that that article is in the
+current group, while it uses the @code{Message-ID} otherwise. However,
+some news servers, e.g., ones running Diablo, run multiple engines
+having the same articles but article numbers are not kept synchronized
+between them. In that case, the article number that appears in the
+@code{Xref} header varies by which engine is chosen, so you cannot refer
+to the parent article that is in the current group, for instance. If
+you connect to such a server, set this variable to a non-@code{nil}
+value, and Gnus never uses article numbers. For example:
+
+@lisp
+(setq gnus-select-method
+ '(nntp "newszilla"
+ (nntp-address "newszilla.example.com")
+ (nntp-xref-number-is-evil t)
+ @dots{}))
+@end lisp
+
+The default value of this server variable is @code{nil}.
+
@item nntp-prepare-server-hook
@vindex nntp-prepare-server-hook
A hook run before attempting to connect to an @acronym{NNTP} server.