From owner-freebsd-questions@FreeBSD.ORG Sat Jan 6 16:25:04 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 DDCCC16A407 for ; Sat, 6 Jan 2007 16:25:04 +0000 (UTC) (envelope-from fbsd06@mlists.homeunix.com) Received: from mxout-03.mxes.net (mxout-03.mxes.net [216.86.168.178]) by mx1.freebsd.org (Postfix) with ESMTP id AB5B613C457 for ; Sat, 6 Jan 2007 16:25:04 +0000 (UTC) (envelope-from fbsd06@mlists.homeunix.com) Received: from gumby.homeunix.com (unknown [87.81.140.128]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTP id 95CC651944 for ; Sat, 6 Jan 2007 11:25:03 -0500 (EST) Date: Sat, 6 Jan 2007 16:25:00 +0000 From: RW To: freebsd-questions@freebsd.org Message-ID: <20070106162500.38b8e50f@gumby.homeunix.com> In-Reply-To: <459FB34A.9000507@infracaninophile.co.uk> References: <00bb01c73134$b061fa60$0a32a8c0@rob> <459F0D1B.7090608@tandon.net> <459F1719.9010407@optusnet.com.au> <20070106133209.0cdda901@gumby.homeunix.com> <459FB34A.9000507@infracaninophile.co.uk> X-Mailer: Sylpheed-Claws 2.6.0 (GTK+ 2.10.6; i386-portbld-freebsd6.1) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: Mail being sent from my domain... 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: Sat, 06 Jan 2007 16:25:04 -0000 On Sat, 06 Jan 2007 14:33:46 +0000 Matthew Seaman wrote: > Your reasoning is incorrect. The presence or absence of SPF records > affects how the systems that are the targets of the spam attack work, > and those are not in the control of the spammers. The ability of > a mail system to realise by analysis of SPF records that the mailer > connecting to it is an impostor that has no right to send mail from > the falsely claimed sender address means that the message can be > rejected early during the SMTP dialogue with a 5xx error (ie > permanent delivery failure) even before the body of the message has > been transmitted. > ... > Secondly, you are assuming that the software the spammers use to > inject e-mail is compliant with the various standards (RFCs 2821, > ... Delivery failures are normally generated by the sending server. If you block SPF failures at the SMTP level there are two possibilities. If the sender is a real MTA it will generate a backscatter delivery failure. If it's a spambot or spamming script then it wont, but it wouldn't have anyway, with or without SPF. SPF may help fight spam, but I don't see how it can have a major impact on backscatter when people use 5xx errors.