Glenn Smith wrote:
Someone's just pointed me to http://spf.pobox.com/ which looks like there could be a whole load of impacts to ISPs.
Has anyone really looked in to this and found anything useful out? From our perspective, we only send email out from our server for our domains, so not a huge issue to add them, although a real pain.
But if you think about someone offering dialup, and they have users sending email with the from address as a personally registered domain rather than the ISPs through the ISP mail server it would stop working.
From what I've seen, SPF is much more useful as a "fail" test than as a "pass" test. When you set up SPF, in effect you are saying "Legitimately sent email that claims to be from my domain(s) will come from these IP addresses". The most obvious "fail" scenario is the spammer sending mail via a zombie computer on a broadband connection, with a forged return address of "[EMAIL PROTECTED]". Presuming Yahoo has SPF set up, the receiving mail server or client has a mechanism to check (and cast doubt) on the message. So, as an ISP, the benefit to you with SPF is additional verification of an e-mail's legitimacy.
On the other hand, many major spam houses were quick to add SPF to their won domains. They did this because at first, many people were incorrectly presuming that if an incoiming message passed SPF, it probably wasn't spam. This is not true; passing SPF simply means that the return address in the e-mail probably does belong to the same domain as the host sending it.
We use Delcude Junkmail here. I add a small amount of weight to messages that fail SPF, and neither penalize or reward messages that pass SPF or don't have SPF set up at all.
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