Mail Filtering with Mail::Audit
by Simon Cozens
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Pages: 1, 2, 3, 4
Mail and News
I much prefer reading mailing lists as newsgroups; while a good mail client like mutt can display mail as threaded discussions, I personally prefer navigating in a newsreader. So, how do we gate mailing lists to newsgroups and back? Russ Allbery's News::Gateway module helps do just that - it provides a program called listgate which takes an incoming mailing list message, reformats it as a valid news article, and then posts it to the news server. We can plug this into our mail filter quite easily; assuming we've got the group lists.p5p set up on the local news server and we've configured listgate appropriately, we can just say:
$item->pipe("listgate p5p") if $item->from =~ /perl5-porters/;
Again, if we've got multiple groups, we can use a hash to correlate patterns to groups as we did with mailing lists above.
So much for getting incoming mail to news - what about getting posted articles back into the mailing list? The key to this is in the newsgroup moderation system - when you post to a moderated newsgroup, the article is mailed to a moderator for approval. If we set the moderator of lists.p5p to the list address, we can get our outgoing posts sent to the list. In /usr/news/etc/moderators, you'd say
lists.p5p: perl5-porters@perl.org
Very easy. The only problem is that it doesn't work. Mail messages and news articles have a slightly different format, and some mailing list managers will reject mail messages that look like news articles. So we need to send our message through a clean-up phase first. Instead of sending it to perl5-porters@perl.org, we'll instead send it to news-outgoing@localhost:
lists.*: news-outgoing@localhost
Mail arriving at that account needs to go through another Perl program to clean up and dispatch the outgoing article, and that looks like this:
#!/usr/bin/perl
use News::Gateway;
my $gw=News::Gateway->new(0);
$gw->modules( 'newstomail', 'headers');
$gw->config_line("newstomail /home/simon/bin/news2mail.h");
$gw->config_line("header newsgroups drop");
$gw->config_line("header organisation drop");
$gw->config_line("header nntp-posting-host drop");
$gw->read(*STDIN) or die $!;
$gw->apply();
$gw->mail();
This reads an article from standard input, drops the Newsgroups, Organisation, and NNTP-Posting-Host headers, reformats it as a mail message using the configuration file /home/simon/bin/news2mail.h to find the address, and then sends it. That config file is just a list of newsgroups and the addresses they belong to:
lists.p5p perl5-porters@perl.org
lists.tlug tlug@tlug.gr.jp
lists.advocacy advocacy@perl.org
lists.linux-kernel linux-kernel@vger.rutgers.edu
lists.perl-friends perl-friends@perlsupport.com
So here's the recipe for filtering news to mail and back again:
• Incoming messages
will be trapped by a rule in your mail filter, and be piped to listgate via a line like
$item->pipe("listgate p5p") if $item->from =~ /perl5-porters/;listgate will then post them to your news server, to the group lists.p5p.
• Outgoing articles
will be sent to the moderator address, news-outgoing@localhost for cleanup. The cleanup program will drop unnecessary headers, reformat as a mail message, and then look at the configuration file to determine where to send them on. They'll be sent to the mailing list, and sometime later will be returned to you by mail, to appear in the newsgroup as above.
