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Re: [spf-discuss] Re: DNS record caching the microsoft way

2006-06-10 12:12:40
In 
<Pine(_dot_)LNX(_dot_)4(_dot_)62(_dot_)0606101153580(_dot_)22249(_at_)sokol(_dot_)elan(_dot_)net>
 "william(at)elan.net" <william(_at_)elan(_dot_)net> writes:

On Sat, 10 Jun 2006, Julian Mehnle wrote:

Wayne Schlitt wrote:

The point is that the text included in the RFC gives you a clear idea
of what MS thinks about what is reasonably cached and that was the
original subject. [...]

Agreed.  But the _real_ point, I think, is that MS do not only not _cache_
records with the "s,l,o,h" macros, but do not _use_ them at all.  Which is
bad.

While it would be better if all (valid) SPF records were evaluated,
there is nothing that says that the receiver can't pick and choose
which records are worth their time.

Why did MS say they are doing this way again?

Because the volume of email that hotmail receives makes it very hard
for them to do SPF checks in real-time.  My understanding is that,
instead, they have a backend process that is given the most common
<domain> and <ip> pairs, the backend creates a "cache" of the results,
and this cache periodically gets rolled out to the hotmail
MTAs. Actually, it is all a little more complicated than that.

There was a presentation at this April's Email Authentication Summit
on how Hotmail has integrated SenderID into their system.  See:

http://www.emailauthentication.org/summit2006/agenda.html
http://www.emailauthentication.org/summit2006/pdfs/3MSN.pdf
http://boss.streamos.com/wmedia/worktank/eas/eas2_emails-trustworthy-score.asx


-wayne

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