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From "Noel J. Bergman" <n...@devtech.com>
Subject Permanent errors from transient DNS issues?
Date Fri, 24 Nov 2006 16:16:43 GMT
Norman,

> Noel J. Bergman schrieb:
> > -1
>
> > The handling of this condition as temporary was very intentional, and
> > in no way accidental.  This is a not uncommon problem.  The DNS can be
> > wrong, and later corrected.  The problem is ascertaining whether a
> > domain is non-existent for real (there is no registration record) or
> > because of a temporary DNS configuration error.
> >
> > Consider the debate within the SPF council regarding whether or not
> > NXDOMAIN was to be treated as a PermError or TempFail.

> This was not the final solution. See revision 478589

I am not happy with the change.  As I read it, r478589 is a bit better only if the local DNS
server is down.  That's only one of several DNS related issues that can result in failure.

Consider http://www.mhonarc.org/archive/html/spf-discuss/2005-05/msg00327.html.  I do consider
the author of that particular e-mail to wrong because the intent of the SMTP specification
is to put a very high degree of reliability on the delivery of mail.  We bias decisions to
ensure delivery.  But the point is for you to read the real-world examples of DNS failure
given to him as examples.  And, FWIW, I have seen similar errors and had mail lost by qmail
that would not have been lost by JAMES.

I am OK with optional filters for rejecting mail in-protocol if the MAIL FROM or even REPLY-TO
domains are invalid (even temporarily), but I am *not* OK with hardcoding the change you are
making to bounce mail because there is a transient DNS glitch on the delivery side.

Do you understand now?

	--- Noel



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