spf-discuss
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Re: [spf-discuss] Mail Forwarding Question

2006-02-27 14:33:54
On Mon, 27 Feb 2006, John Kelly wrote:

Then I wonder why domain owners would try to protect their identity
with an RFC large ISPs will ignore.

Large ISPs have other methods that benefit from economies of scale.  For
instance, AOL puts IPs on temporary blacklists based on behaviour.  But it is 
helpful when large ISPs publish SPF so that us little guys can easily
reject forgeries of their domain.  It is technically very cheap to require
end users to use SMTP AUTH to send mail from the ISP domain - but 
a big education campaign is needed to get users to actually put in
the proper outgoing SMTP configuration.  Hence, big ISP SPF records
tend to be lax (don't end in -all).

A large ISP has to balance the benefit of cheaply rejecting forgeries
detected by SPF with the cost of providing the necessary configuration
options for users to handle non-SRS forwarders.  (Or else decide
to use their weight to force forwarders to use SRS - but that is kind
of like M$ using their weight to force everyone to publish PRA records.)

-- 
              Stuart D. Gathman <stuart(_at_)bmsi(_dot_)com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

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