RE: [Asrg] CRI Header

At 11:08 PM 6/14/2003 -0400, Eric D. Williams wrote:

>On Monday, June 09, 2003 2:39 PM, Yakov Shafranovich
>[SMTP:research@solidmatrix.com] wrote:
>8<...>8
> > HOWEVER, the same section states:
> >
> > "Whenever an SMTP transaction is used to send a DSN, the MAIL FROM command
> > MUST use a NULL return address, i.e., "MAIL FROM:<>"."
>
>A proper intepretation of that statement requires its full context.  The 
>intent
>is to prevent message looping.  As such the CRI or other systems SHOULD 
>ensure
>that specfied addresses do not violate that tenet.
>
>
>    The envelope sender address of the DSN SHOULD be chosen to ensure
>    that no delivery status reports will be issued in response to the DSN
>    itself, and MUST be chosen so that DSNs will not generate mail loops.
>    Whenever an SMTP transaction is used to send a DSN, the MAIL FROM
>    command MUST use a NULL return address, i.e., "MAIL FROM:<>".
>
>
> > That means that C/R systems such as yours MUST support the empty return
> > path (<>).
>
>No it does not, IMO, given the full context of the requirement.

We were considering implementing CRI within the extension framework of 
DSNs. DSNs require the return path to be <>, so any system that would use 
such protocol in this matter, would require <> as well. I didn't not mean 
that ALL C/R systems will use it - thank you for pointing this out.

Someone pointed out that DSNs might not be the best solution, since it is 
intended to be a one-way notification, as opposed to CRI where the 
challenge is intended to be responded to and there is also an issue of all 
systems that do not support CRI but support DSNs. I also contacted Keith 
Moore who wrote the DSN RFCs for his opinion, so we'll see how this one 
will fall out. DSNs have an advantage of having an ESMTP extension defined. 
In any case, we might want to take a look at the MIME type of 
"multipart/report" within which DSNs operate. This MIME part might be used 
for CRI, patterned after the DSNs structure.

Yakov

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