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Re: Experiment #2 with multiple Reference headers (was References with multipl

2005-01-17 20:53:33

On Mon, 17 Jan 2005, Charles Lindsey wrote:

 "william(at)" <william(_at_)elan(_dot_)net> writes:

Now as has been mentioned, I plan to document these Original- headers in the
Internet draft so if you like to provide some feedback about it, please go
ahead (and note that I already know of number of different programs adding 
these headers without any documentation and draft will try to keep it
primarily as documentation of current practice and explain what these are).

Accidentally I can't find any good way to register with IANA a group of 
like Original- (as common prefix) as RFC3864 specifies only how to do it for
one particular header field. Please suggest what to do about it.

I think that registry is intended for fields that agents might be expected
to recognize and act upon. I doubt any MUA is going to have a
built-in-recognition of any and all fields beginning with "Original-".
Surely they are intended for human consumption, in which case using
"X-Original-xxxxxx" would he just as good, and would break no rules or

Aren't trace fields like "Received:" intended for human consumption too? :)

And in this case, while its primarily trace data for humans for debugging 
it could potentially be used by MTAs, for example to detect complex mail 
loop. Besides that some systems might choose to display "Original-Sender"
or "Original-From" in MUA as well (on part with Sender, From, Resent-From,
Resent-Sender when showing the entities involved in email transmission).

And while use I have seen involves both "X-Original" and "Original-"
(with same header names used afterward) depending on which system was 
doing it, lately "Original-" is becoming more common and I believe if 
it is to be documented in the RFC, it would have to be without "X-".

And its not exactly that it would "break" the registry rule, its just
that currently there is no way to do it and I think that means we'd
have to expand IANA header registry to allow to define certain set of
headers with common prefix or to specifically reserve "prefix" for
use with one type of headers (which are afterward specifically defined).
That generally means either separate draft for IANA or expansion of 
RFC3864 (but I really would prefer header prefix registry by on same page 
at IANA as specific header names registry).

This is useful for more then just "Original-", it can well be argued that
"Resent-" should also part of this header prefix registry as well as "MIME-"
and "Content-" (specific headers for those are defined in documents but
prefix use is reserved) and likely "Envelope-" would fall into this 
category as well for reserving for specific use. Another of my upcoming 
drafts (see is using "Saved-" headers in similar 
way as "Original-" for duplication of existing header data (although I'm 
seriously considering if/how it could be combined with use of "Original-").

William Leibzon
Elan Networks

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