Re: [art] Alissa Cooper's No Objection on draft-ietf-appsawg-mdn-3798bis-15: (with COMMENT)

[Alissa Cooper <[e-mail]>]

> On Nov 30, 2016, at 11:34 AM, Barry Leiba <[e-mail]> wrote:
> 
>> = Section 6.2 =
>> 
>> "Disposition mode (Section 3.2.6.1) can leak information about
>>   recipient's MUA configuration, in particular whether MDNs are
>>   acknowledged manually or automatically.  If this is a concern, MUAs
>>   can return "manual-action/MDN-sent-manually" disposition mode in
>>   generated MDNs."
>> 
>> I see why this is here, but doesn't recommending falsifying these fields
>> put their integrity in question whenever they are set to manual? I mean,
>> why would recipients trust this information if the RFC actually suggests
>> sending a field that lies about an MDN being automatically acknowledged?
> 
> This comes from my pushing on the point, and is the only reasonable
> mediation we could come up with.  Here's the summary of the
> discussion:
> 
> - I don't see any use in having this field at all.  There's nothing
> useful the MDN recipient's mail system can do with it, and it only
> serves to expose information about the MDN sender's configuration
> unnecessarily.  I'd rather see it removed entirely.
> 
> - That said, it's been required from the beginning, so (1) all
> existing implementations send it, (2) existing implementations expect
> to receive it, and are likely to consider the MDN invalid if it's not
> present, and (3) implementations are not expected to be reworked to
> match this spec if we should change that now.
> 
> - Because of (2) above, we can't just recommend not sending it.
> Further, the field wasn't designed to be extensible, so we can't use
> some value such as "unknown" -- that would most likely have the same
> effect as in (2), that implementations would consider those to be
> invalid MDNs.
> 
> - The only thing that leaves is recommending a "standard" value to
> send if you don't want to expose the real information.  That value has
> to be one of the two defined values, and "manual" is the less bad
> option (as opposed to telling the recipient's system that you're
> configured to automatically send MDNs).
> 
> - And because of the first bullet above (that there's nothing useful
> to be done with this information anyway), lying about it doesn't hurt
> anything.
> 
> It's a bad, but usable solution to an unfortunate problem.

Got it, thanks for the explanation.

Alissa

> 
> Barry