Date: Sat, 6 Jan 2007 16:25:00 +0000 From: RW <fbsd06@mlists.homeunix.com> To: freebsd-questions@freebsd.org Subject: Re: Mail being sent from my domain... 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>
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On Sat, 06 Jan 2007 14:33:46 +0000 Matthew Seaman <m.seaman@infracaninophile.co.uk> 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.
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