[Mimedefang] Leveraging rfc-ignorant.org

[Jan-Pieter Cornet]

On Sun, Jun 08, 2008 at 09:54:01PM +0200, Andrzej Adam Filip wrote:
> >> Consider blocking in replies to "RCPT TO:" so you can exclude some
> >> destination addresses from the check (e.g. postmaster and abuse).
> >
> > Well, I'm figuring that if they were doing "postmaster" and "abuse"
> > properly, they wouldn't be listed in rfc-ignorant.org to begin with,
> > right?

rfc-ignorant.org is about not *receiving* mails to postmaster/abuse.
(among others)

> I suggest to allow contacting postmaster at your.domain so delivery
> (blocking) "issues" can be solved without using phone/fax.
> 
> Do expect false positives with *ANY* DNSBL.

Especially with rfc-ignorant :) See
http://lists.roaringpenguin.com/pipermail/mimedefang/2004-September/024641.html
etc

That said, if you have a "toy" domain, you can usually get away with
it, blocking everything even to postmaster/abuse. If you're somewhat
more serious about your domain, you should allow for some reasonable
fallback (that doesn't require jump-through-hoops web stuff).

To answer your original question: since rfc-ignorant is domain-based,
you cannot use the md_relay_is_blacklisted functions. So you'll have
to roll your own, but it's pretty trivial. Eg:

sub filter_recipient {
    my ($recipient, $sender, $ip, $hostname, $first, $helo,
        $rcpt_mailer, $rcpt_host, $rcpt_addr) = @_;

    if ( $sender =~ /\@([\w.-]+)$/ ) {
	my $sender_domain = $1;
	if ( gethostbyname("$sender_domain.whois.rfc-ignorant.org") ) {
	    return('REJECT', "$sender_domain is RFC-ignorant");
	}
    }
    return('CONTINUE', 'OK');
}

(note: untested!)

-- 
Jan-Pieter Cornet <johnpc at xs4all.nl>
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