From owner-freebsd-questions@FreeBSD.ORG Thu Jan 4 00:21:31 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 DDBB816A403 for ; Thu, 4 Jan 2007 00:21:31 +0000 (UTC) (envelope-from ryallsd@gmail.com) Received: from nf-out-0910.google.com (nf-out-0910.google.com [64.233.182.186]) by mx1.freebsd.org (Postfix) with ESMTP id 7903A13C45E for ; Thu, 4 Jan 2007 00:21:31 +0000 (UTC) (envelope-from ryallsd@gmail.com) Received: by nf-out-0910.google.com with SMTP id x37so7326911nfc for ; Wed, 03 Jan 2007 16:21:30 -0800 (PST) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=LA+4NfJWFI4fF2xrQqGtgACm/+1tcmv+Su8k7WSMCDq4/qMPAcM5gD+qHXMvLjVWKD6Gxfb7oBwqT4//5I8TyjePsjL6ttMY8JU2ovIvzht/H1+OKT1wx2JXqjzn0GSpNiDOz52DSMfwAsL2Awz8skdLLNte4rYDi1IEhXhZncY= Received: by 10.82.114.3 with SMTP id m3mr1841964buc.1167868552839; Wed, 03 Jan 2007 15:55:52 -0800 (PST) Received: by 10.82.154.7 with HTTP; Wed, 3 Jan 2007 15:55:52 -0800 (PST) Message-ID: Date: Wed, 3 Jan 2007 15:55:52 -0800 From: "Derrick Ryalls" To: FreeBSD-questions MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Cc: Subject: 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 00:21:31 -0000 This is perhaps off topic, but all machines in question are running FreeBSD :) Every day I get dozens of failed email notifications in the form of: UNDELIVERABLE MAIL Your message to the following recipients cannot be delivered: : webmail.hansenet.de [213.191.73.2]: RCPT TO: <<< 550 RCPT TO: User unknown This user Unknown message is due to my server rejecting a mail to my domain (my domain is not alicedsl.de) for an Unknown user. Doing some reading, it appears that in a perfect system where there is only 1 email server per domain, I won't recieve these messages since during the whole email conversation I will tell the person talking to me that I don't know of that account and no extra email is generated. 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? If my guesses are incorrect, then what is actually going on and how do I stop the flow?