rfc1036 December 1987

3.7.  Checkgroups
    The message body is a list of "official" newsgroups and their
    description, one group per line.  They are compared against the list
    of active newsgroups on the current host.  The names of any obsolete
    or new newsgroups are mailed to the user "usenet" and descriptions
    of the new newsgroups are added to the help file used when posting
    news.