If the NNTP server is the local host name (exactly the same as the
value returned by the function system-name), and the variable
gnus-nntp-service is nil, GNUS looks up the local news spool of
your machine directly instead of NNTP (see section NNTP Service).
It may be a good idea not to use NNTP if you wish to reduce network traffic (even if an NNTP server is running on the local machine) though commands for retrieving articles by Message-IDs may take longer or not work at all. See section Referencing Articles, to refer to articles by the Message-IDs, and see section Local News Spool Specific Variables, for more information on the restrictions.