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Re: [dkim-ops] [Q] _adsp._domainkey.klunky.co.uk - is this correct, and should I use it

2011-02-14 09:24:41
My quick comments for anyone considering ADSP:

ADSP is great if 100% of the mail you send from your domain is actually 
compliant to ADSP's strict definition of what an "author domain signature" is 
(and "discardable" is fine if you don't mind losing mil that traverses mailing 
lists).  So that's really the starting point for anyone considering ADSP.  But 
the second step is to go out and get a feedback loop from some intermediaries 
or mailbox providers.  Without visibility into what is happening with your mail 
after an authentication result is established, you are blind to your 
deliverability (which is not healthy because your false-positive rates could 
spike and you'd never know).

Some day ADSP will have to be "fixed" or "replaced" with something more useful 
to a broader set of use cases, and more usable in terms of facilitating the 
right kind of reporting/feedback loops.  But that's a story for another day ;-)

In the meantime, we are getting utility from ADSP.

-- Brett


On Feb 13, 2011, at 9:42 PM, Jim Fenton wrote:

On 02/09/2011 07:25 AM, John Levine wrote:
However, I did not know about the _adsp_ record.  I know that
dkim-filter will look for this.

    i) Should I add one.
Unless your name is Paypal, please don't.

ADSP is debatably of some use for the elite group of senders whose
domains are widely forged, and whose recipients are likely to suffer a
significant loss if they're fooled by the forgeries.  For the other
99.999% of senders, it's just a way to ensure that some of your real
mail is thrown away.


A dissenting opinion:

I have been using ADSP "dkim=all" for quite some time from this domain 
and have had no indication that any of my mail has been dropped.  Note 
that my mail usage patterns are consistent with dkim=all (messages 
always go through my MTA that does the signing), but I do send through 
mailing lists such as this one that undoubtedly invalidate my DKIM 
signature.

"dkim=discardable" is really intended for the domains John describes: 
transactional domains like PayPal that (1) sign all their messages, (2) 
don't generally send through mailing lists, etc. that invalidate their 
signatures, and (3) would rather that a valid message be dropped than to 
have a spoofed message make it through.

I'm not trying to kick off a new debate but thought that I should point 
out that John's opinion isn't universally held.

-Jim
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