OT: What is "SPF" ?

David Relson relson at osagesoftware.com
Wed Aug 25 21:46:22 CEST 2004


On Wed, 25 Aug 2004 15:37:44 -0400
Dan Deward wrote:

> It's a free spam filter for Exchange. http://spf.pobox.com/  (a.k.a
> Sender Policy Framework)

Hi Dan,

That's not my understanding at all.  It's a sender verification method
that helps to weed out bogus "from" addresses.  

Given a message from "person at mail.example.com", SPF is a way to check
with "example.com" that "mail.example.com" really is a valid mail
sending machine.  Setting it up at the sending end requires some minor
text changes to the DNS records (to identify the valid sending
machine(s)).  Successful use at the receiving end requires that senders
have the DNS changes.  

Using SPF may be useful as a spam filter, but only if _all_ senders have
it implemented.  If all valid senders implement SPF, then forged
messages from zombie machines will be "invalid" (and can be rejected).

The above is my understanding at present.  Corrections are welcomed :-)

Regards,

David



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