From owner-freebsd-questions@FreeBSD.ORG Fri Apr 6 14:43:51 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id EFB7316A401 for ; Fri, 6 Apr 2007 14:43:51 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.freebsd.org (Postfix) with ESMTP id C3FC813C455 for ; Fri, 6 Apr 2007 14:43:51 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id 13A005D65; Fri, 6 Apr 2007 10:43:51 -0400 (EDT) X-Virus-Scanned: amavisd-new at codefab.com Received: from pi.codefab.com ([127.0.0.1]) by localhost (pi.codefab.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KEQREGzVQrT7; Fri, 6 Apr 2007 10:43:46 -0400 (EDT) Received: from [192.168.1.3] (pool-68-161-116-136.ny325.east.verizon.net [68.161.116.136]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pi.codefab.com (Postfix) with ESMTP id ED7EA5C54; Fri, 6 Apr 2007 10:43:45 -0400 (EDT) Message-ID: <46165C9A.7040906@mac.com> Date: Fri, 06 Apr 2007 10:43:38 -0400 From: Chuck Swiger User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 To: Christopher Martin References: <05df01c7783b$a0dd74e0$d315a8c0@SAURON> In-Reply-To: <05df01c7783b$a0dd74e0$d315a8c0@SAURON> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-questions@freebsd.org Subject: Re: Receiver (To/CC envelope fields) addresses verification against LDAP/Active Directory in sendmail X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Apr 2007 14:43:52 -0000 Christopher Martin wrote: > Spam with randomly generated recipient addresses is draining our mail > system's life away, and it seems the easiest way would be to verify the > receiving party's/parties' address against Active Directory and then > TEMPFAIL any mails that don't have any valid internal mails (rejects would > allow directory harvesting to work). > > Our network has a frontline mail filter system running FreeBSD 6.2, > Sendmail, milter-regex, Spam Assassin 3.1.8 and Clam AV, which delivers to > our internal Exchange server via a smarthost entry. You don't seem to mention using greylisting-- that will return a 4xx temp failure for all initial connections (except from sites which have been whitelisted). Only if the sender retries will the mail go through-- this works great against dictionary-style attacks. -- -Chuck