From: Alex van den Bogaerdt (alexergens.op.het.net)
Date: Fri Jan 09 2004 - 15:10:50 CST

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On Fri, Jan 09, 2004 at 03:57:27PM -0500, Nick Fisher wrote:

> So, without SRS (http://spf.pobox.com/srs.html) being implemented properly
> on EVERY mail server on the net, SPF can't work 100% properly. It would
> still be useful in something like SpamAssassin where the result was given a
> weight but if left as an absolute it's almost going to guarantee that some
> of your mail will be incorrectly (due to forwarding) be classified as spam.

The user that forwards the mail will find out that the final destination
is using SPF and will have to stop forwarding in the current manner.

Forwarding could be done in an entirely different way. For instance,
the original message could be attached to a new message (originating
from the forwarder) to the final destination.

> Am I missing something here? How is SPF going to reliably work when SRS
> isn't standard yet?

Strictly speaking, it *is* working reliably. The final destination has
a policy to trust the policy of the originating domain. The originating
domain has a policy that noone but them should be sending mail with their
domain in the headers.

You probably do not agree with the policy but this doesn't mean the
protocol doesn't work reliably.

Either the originator of the mail has to convince its ISP to change
its policy (use ?all, not -all) or the forwarding user has to find
a way to not send out mail with 3rd party headers (for instance using
SRS, or by encapsulating the message).

cheers,
Alex
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