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Re: SPF and SMTP 551/251 result codes.

2004-03-26 15:00:16
On Fri, 2004-03-26 at 16:55 -0500, Meng Weng Wong wrote:

What's been proposed is

  A X) B -> C

But it seems easier to just let the failure occur like with

  A -> B X) C

Not quite. Because I'm proposing that what should happen is _not_ a
rejection but a redirection. I'm suggesting that SPF-publishing senders
should _not_ bounce mail upon seeing a 551 response code, but should
send the mail to the address which was provided.

It seems easier all around if the rejection happens at C than at B.
After all, it's A and C who are doing SPF, and B is the "innocent" ---
if B is going to start rejecting SPF mail, it looks like it's getting
involved just to make a point.

It's getting involved to offer a solution in the _simplest_ possible way
for itself.

Commercial forwarders are going to have to do SRS anyway, because
they're in the business of making things work, not making things break.

The idea of making 551-obedience mandatory for SPF publishers makes
things work _without_ such onerous requirements on forwarders. Isn't
that a good thing?

At least we could say that domain publishing SPF 'SHOULD' react to a 551
response to a 'RCPT TO:' by sending the mail to the indicated address,
rather than bouncing. 

-- 
dwmw2


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