From owner-freebsd-questions@FreeBSD.ORG  Sun Mar 24 16:59:16 2013
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115])
 by hub.freebsd.org (Postfix) with ESMTP id A55323E8
 for <freebsd-questions@freebsd.org>; Sun, 24 Mar 2013 16:59:16 +0000 (UTC)
 (envelope-from Lena@lena.kiev.ua)
Received: from lena.kiev.ua (lena.kiev.ua [82.146.52.81])
 by mx1.freebsd.org (Postfix) with ESMTP id 74AC26CD
 for <freebsd-questions@freebsd.org>; Sun, 24 Mar 2013 16:59:16 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lena.kiev.ua;
 s=3; 
 h=Content-Type:Mime-Version:Message-ID:Subject:To:From:Date;
 bh=HnM0RXDr1olA9E1jXK85LYeFhzi1SVBVXJXZCQoSLBA=; 
 b=g5xEEFsPdW9JW0yYnMpKCVSIHASVSkaTqmjQKY4LfKNuhq0qbNXOahs/XWLCajZim+15l5dyc0vnMHQijpBkCEVkBDvBJDkOTQNA6nwzQ0+CamlWdaolS/0ortj1X1Y5ANJLVhqcvH9/5wOV9hq/TnDPGpc2xWM0HO7/P6wrRLw=;
Received: from ip-384c.rusanovka-net.kiev.ua ([94.244.56.76]
 helo=bedside.lena.kiev.ua)
 by lena.kiev.ua with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256)
 (Exim 4.80.1 (FreeBSD)) (envelope-from <Lena@lena.kiev.ua>)
 id 1UJoGJ-000Jtc-9P
 for freebsd-questions@freebsd.org; Sun, 24 Mar 2013 18:59:16 +0200
Received: from bedside.lena.kiev.ua (localhost.lena.kiev.ua [127.0.0.1])
 by bedside.lena.kiev.ua (8.14.6/8.14.5) with ESMTP id r2OGx9Zt003651
 for <freebsd-questions@freebsd.org>; Sun, 24 Mar 2013 18:59:09 +0200 (EET)
 (envelope-from Lena@lena.kiev.ua)
Received: (from lena@localhost)
 by bedside.lena.kiev.ua (8.14.6/8.14.5/Submit) id r2OGx9P7003650
 for freebsd-questions@freebsd.org; Sun, 24 Mar 2013 18:59:09 +0200 (EET)
 (envelope-from Lena@lena.kiev.ua)
Date: Sun, 24 Mar 2013 18:59:09 +0200
From: Lena@lena.kiev.ua
To: freebsd-questions@freebsd.org
Subject: Re: Client Authentication
Message-ID: <20130324165909.GC913@lena.kiev>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.4.2.3i
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 24 Mar 2013 16:59:16 -0000

> How about refusing to
> relay mail from addresses in a good DNSBL?

Bad idea. Legitimate users connecting from dynamic IP-addresses is normal.
DNSBLs list a dynamic IP-address permanently
or for long time after a zombied Windows spewed spam from it.
Some DNSBLs warn about that explicitly, for example:
http://www.spamhaus.org/zen/

| Caution: Because ZEN includes the XBL and PBL lists, do not use ZEN
| on smarthosts or SMTP AUTH outbound servers for your own customers
| (or you risk blocking your own customers).