From owner-freebsd-questions@FreeBSD.ORG  Sat Jan  6 13:32:13 2007
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Date: Sat, 6 Jan 2007 13:32:09 +0000
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Subject: Re: Mail being sent from my domain...
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On Sat, 06 Jan 2007 14:27:21 +1100
Colin House <col-h@optusnet.com.au> wrote:

> Check out http://openspf.org - implementing SPF will help prevent 
> spoofed emails from being delivered and will start to cut down on the 
> "backscatter"

This often claimed, but I don't really see how it's going to help much.

Any benefit relies on an initial MTA/MSA refusing to relay for domains
that don't set the correct SPF records, i.e. it replies on the security
of MTA's that are owned, controlled or abused by spammers.

On the other hand setting SPF records means that more spam using the
domain will be rejected at the SMTP level. This actually leads to more
backscatter.