Date: Thu, 21 Mar 2002 09:43:50 -0700 From: Ian <freebsd@damnhippie.dyndns.org> To: freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: using dnsbl to filter email Message-ID: <B8BF5BD6.B566%freebsd@damnhippie.dyndns.org> In-Reply-To: <004001c1d087$96018950$0301a8c0@blowfish>
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> From: "Hervey Wilson" <herveyw@dynamic-cast.com>
> Date: Wed, 20 Mar 2002 19:22:09 -0800
> To: "Kutulu" <kutulu@kutulu.org>, <freebsd-stable@FreeBSD.ORG>
> Subject: Re: Postfix SMTP server: errors from mx2.FreeBSD.org[216.136.204.119]
>
> Well that would likely explain the failures !
>
> Can anyone recommend an alternative ?
I'm currently auditioning a variety of the dnsbl services available. Here's
an overview of many of the current services:
http://www.declude.com/junkmail/support/ip4r.htm
ORDB seems to be very good as an open relays blocker, and I'd estimate that
alone blocks about 50-60% of the spam on a user's group server I admin. The
other lists that look good to me right now (and have reasonable-seeming
policies about listing and delisting, in my opinion) are bl.spamcop.net, and
relays.osirusoft.com with a caveat that you have to ignore their dialups
listings because they include DSL and cable modem users. (As a cable modem
user who runs a responsible secure mail server, I resent being listed.)
If you run a server that handles mail for multiple users, deciding to use
any BL service can be problematic, there is always collateral damage with
such lists, it seems. And you haven't been flamed until you've been flamed
by a client/user for "censoring" their email. :-)
I'm currently working on a sendmail milter that consults a variety of BLs
(configurable) and adds an X-RBL-Advice: header to the mail to report the
results to the end user. The users can then have their email clients filter
based on the presence of reporting from the BLs that they decide to trust
for themselves. It even works when the mail has been forwarded thru several
accounts or via a mailing list (it's nice to have no spam in my freebsd list
folders every morning now).
-- Ian
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