Mail::Summary::Tools::Downloader::NNTP - Get NNTP articles and their thread roots.

	use Mail::Summary::Tools::Downloader::NNTP;

	my $downloader = Mail::Summary::Tools::Downloader::NNTP->new(
		server => "nntp.perl.org",
		cache  => $article_cache,
		fetch_recursively => 0,
	);

	my $mgr = Mail::Box::Manager->new;
	my $mbox = $mgr->open( "foo" );

	$downloader->download(
		group   => "perl.perl6.language",
		from    => 10000,
		to      => 11000,
		mailbox => $mbox,
		extra_mailboxes => \@extra,
	);

This utility makes downloading mailing list archives from an nntp server into a mailbox trivial.

Messages whose message ID is already in any of the mailboxes are not downloaded.

Additionally, message IDs listed in the References header will also be fetched if fetch_recursively is on (the default).

Since Mail::Box::Thread::Manager can thread messages from multiple mailboxes this one can download the next batch of articles with fetch_recursively enabled, and using a log-rotation like mechanism delete older mailboxes without fear of breaking the threads, at the cost of some redundant downloads.