From owner-freebsd-questions@FreeBSD.ORG Thu Jan 4 00:55:09 2007 Return-Path: X-Original-To: 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 ABF1C16A403 for ; Thu, 4 Jan 2007 00:55:09 +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 6770413C44C for ; Thu, 4 Jan 2007 00:55:09 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id D2CB55EDD; Wed, 3 Jan 2007 19:55:08 -0500 (EST) 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 M29RgmFa4OG1; Wed, 3 Jan 2007 19:55:06 -0500 (EST) Received: from [192.168.1.251] (pool-68-161-114-230.ny325.east.verizon.net [68.161.114.230]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pi.codefab.com (Postfix) with ESMTP id 550C85CE2; Wed, 3 Jan 2007 19:55:06 -0500 (EST) Message-ID: <459C505F.1070401@mac.com> Date: Wed, 03 Jan 2007 19:54:55 -0500 From: Chuck Swiger User-Agent: Thunderbird 1.5.0.9 (Windows/20061207) MIME-Version: 1.0 To: Derrick Ryalls References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: FreeBSD-questions Subject: Re: Is there a solution for 550 User Unknown mails 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: Thu, 04 Jan 2007 00:55:09 -0000 Derrick Ryalls wrote: [ ... ] > With secondary mail servers, I am accepting mail for other domains, > and then forwarding them on. It is my belief that acting as a > secondary mail server is what is causing me to receive all these > errors. What I believe is happening is that for whatever reason the > spammer is talking to my email server for a domain I am secondary on. > I accept the mail and finish the conversation. I then talk to the > main email host to let them know of the email I got for them. The > master host responds with 550 User Unknown as it should. Being the > good little secondary email server I am, I try to respond to the > sender that they got the wrong address, which turns out to be fake. > > Assuming that my guessing is correct, is there any way to stop this > flood of reject emails short of not being a secondary server for > anyone? Your assumptions are basically right. The best way to deal with this is to make the secondary MX you run aware of which email addresses are valid and which are not, so it can reject misaddressed mail rather than accepting it and then having to bounce it later. Setting this up via LDAP, NIS, or whatever might be possible but it typically is difficult. Intermediate solutions include using greylisting or creating a manual blacklist of frequently-spammed invalid accounts which you reject immediately. -- -Chuck