Re: delivered-to format (was: Re: Fwd: New Version Notification for draft-crocker-email-deliveredto-05.txt)

On 8/9/2021 1:41 PM, Rolf E. Sonneveld wrote:
>> The key unanswered question is what the "audience" for the header 
>> content
> +1
> 
> A nice example of the proverbial solution in search of a problem.


 From the Introduction, what about this is insufficiently clear or complete?

> Given aliasing, mailing lists, and the like, the transit of a message
> from its author to a final recipient might include a series of
> submission/delivery events. Also, the delivery process can produce
> local address transformations. It can be helpful for a message to
> have a common way of indicating each delivery in the handling
> sequence, and to include each address that led to the final delivery.
> This can aid in the analysis of a message's transit handling. An
> additional use can be for detecting a delivery sequence loop. With a
> loop, the same copy of a messages transits the same email address
> more than once. This is different from having the message simply
> transit the same MTA more than once, which might be necessary, such
> as when it is processed through a mailing list; an MTA services many
> addresses. It is also different from having two copies of the same
> message arrive at the same, ultimate mailbox, having been originally
> posted to two different addresses.
> 
> Delivering the same copy of a message more than once, to the same
> address, is almost certainly not an intended activity. An example of
> a problematic arrangement would be to send a message to mailing list
> listA, where listA contains an entry for listB, and listB contains an
> entry for listA. The message will enter an infinite loop. Loop
> detection for email can be a complicated affair. The Delivered-To
> header field provides helpful information with a definitive
> indication that this copy of a message has been delivered to a
> specific mailbox.




-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net