Re: Cascaded Rewriting

On Wed, 2005-04-13 at 10:19 +0200, Stephan Menzel wrote:
> Am Mittwoch, 13. April 2005 10:14 schrieb David Woodhouse:
> > This is what happens when you rewrite addresses _even_ when they don't
> > need rewriting. Instead, you could rewrite _only_ when the mail would
> > get an SPF 'fail' result, and then the next hop is known to reject for
> > that failure.
> 
> Does that mean, one would have to do that check every time one would rewrite 
> an adress? Seems quite expensive to me. Certainly not an option for us here.

Well, you very rarely have to perform an SPF check. As Mark pointed out,
such a check should be equivalent to checking that the sender domain is
in class w, or accept_domains, or whatever your MTA's equivalent is. SPF
is approximately a way to advertise your MTA's intended accept_domains
via the DNS. (Not totally accurate, but near enough for government
work.)

Thus the check can be performed entirely locally and very fast.

S.

-- 
Shevek <[email protected]>