Subject: Re: [ietf-dkim] [dkim-ops] Q: "dkim=discardable"

From: Douglas Otis <[email-masked]>
Date: Thu, 30 Oct 2008 10:59:09 -0700

On Oct 30, 2008, at 9:26 AM, John R Levine wrote:

>> I think most of the likely candidate domains for using  
>> "discardable" would disagree with your assertion John.
>
> Then I have to say that they don't understand what discardable  
> means. Really, it says feel free to throw our mail away if you have  
> the least doubt about it.  This chronic misconception is the main  
> reason that I doubt that discardable will be useful in practice,  
> since only a small fraction of people who assert it will truly  
> understand what they've said.

The term "discard" in RFC 5321 is used to mean the silent dropping of  
information.

In the prior note you said "It's really only useful for banks and  
places like Paypal sending out notices about accounts, not for any  
domain with individual users."

As Michael suggested, these domains will not want to have their  
messages silently discarded.

The term "discardable" suggests permission to violate RFC 5321 Section  
2.1 MUST accept responsibility for either delivering the message or  
properly reporting the failure.  This same MUST is echoed in Section  
3.6.3 , 4.4 and 6.1.  Section 6.2 provides advice on making an  
exception.

ADSP will affect _all_ messages from the domain.  Few customers will  
welcome messages from similar domains by the same institution.   
Customers that have opted to go paperless will be negatively affected  
by "discardable" since this affects all communications, even those  
considered extremely important.  Unless DKIM signatures are so robust  
that _any_ type of failure provides very high confidence that the  
messages are seriously fraudulent, then the silent discard is not the  
best choice.  If some institution ever had a problem with their DKIM  
signatures, how will they become aware of the problem when _all_ their  
messages are being silently discarded?

At least two people on the DKIM list suggested that this term would be  
problematic.  Instead of "Discardable",  "Dismissible" would not imply  
that not reporting a failure is now allowed.

-Doug
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From: Stephen Farrell <[email-masked]>
Date: Thu, 30 Oct 2008 18:38:28 +0000

Doug,

That was discussed at length in the WG and we ended up
where we ended up.

I'm sure you'll make the point again in IETF LC, (which is
entirely fine), but we don't need to revisit the topic on
this list, so please stop raising it here.

If you think you have some compelling reason that we
should discuss it on-list again, feel free to mail
Barry and I off-list. However, I'm pretty sure I'll
not be convinced from what I've seen to date.

Thanks,
Stephen.