may be any newsgroup name with hierarchies delimited by C<.>.
For example, the newsgroup for L<mailto:meta@public-inbox.org>
is: C<inbox.comp.mail.public-inbox.meta>
may be any newsgroup name with hierarchies delimited by C<.>.
For example, the newsgroup for L<mailto:meta@public-inbox.org>
is: C<inbox.comp.mail.public-inbox.meta>