Re: [apps-discuss] Trace headers, was Adoption of draft-kucherawy-received-state?

["John R. Levine" <[e-mail]>]

>> http://www.iana.org/assignments/mail-parameters, but as far as
>> I can tell, there's no registry of trace headers.
>
> There is no registry of trace headers because there are, and
> have been since RFC 821, only two of them: "Received:" and
> "Return-path:".

If you believe what the RFCs say, there are many more trace headers than 
those two.  RFC 5322 makes a special case of Resent-foo: fields, but they 
act an awful lot like trace headers.  RFC 5451 says that 
Authentication-Results "should be treated as a Trace Field."  RFC 5436 
says "The 'Auto-Submitted' header field is considered a 'trace field'". 
RFC 4408 says that "The Received-SPF header field is a trace field."  RFC 
5518 says "VBR-Info is a 'trace header field'". That horse left the barn a 
long time ago. RFC 5537 also lists a bunch of trace fields for usenet, 
which isn't mail, but it might be a good idea to reserve them to avoid 
collisions.

>  I'm suggesting that the time may have come to
> add one or more rather than continuing to overload "Received:".

It's certainly time for a trace field registry.  And I suppose that if we
have one, adding new trace fields isn't that big a deal.

R's,
John