Re: Fwd: New Version Notification for draft-crocker-email-deliveredto-05.txt

On Fri 13/Aug/2021 04:49:44 +0200 John Levine wrote:
> It appears that Ned Freed  <[email protected]> said:
>> It's also different in that the use of the field in those MTAs is strictly for
>> loop detection, which makes the format a local matter. The draft aims for a
>> different - and in some cases disjoint - logging usage, which really calls for
>> a common syntax.
> 
> As far as we know, all of the existing usage is for loop detection, so it would
> be reasonable to say the contents of the header is a token or sequence of tokens
> with semantics local to the MTA that adds the header.  I suppose we could say something
> like what we say with Message-ID, to use a local domain to avoid collisions.
> 
> What is not reasonable is to overload this existing header with new, incompatible
> semantics and no way to tell the difference.


Without formal overloading, there is no reason to exclude the 
possibility that an MTA records (virtual) mailbox addresses in that 
field.   Local MTA scripts can use the values of Delivered-To: fields, 
if they can be interpreted correctly.  Also MUAs can take advantage of 
any mailbox values found there, as a sponger.  For example, 
Thunderbird has a configuration item named catchAllHeaders which can 
be set to a list such as "envelope-to, x-original-to, to, cc, 
delivered-to".

How about:

     "Delivered-To:"  FWS addr-spec / opaque-tokens FWS CRLF
?

After all, interoperability with MUAs and local operations is one of 
the experimental goals.


Best
Ale
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