What happens with duplicate substitute headers?

Vernon Schryver vjs@calcite.rhyolite.com
Thu Mar 18 22:03:29 UTC 2010

> From: Gary Mills 

> > As required by the SMTP standards, dccm, dccifd, and dccproc ignore
> > "folding whitespace" including "\n\t" in headers.
> > However, dccm, dccproc, and whiteclnt and dccd whitelist files
> > use single lines.  Simply delete the newlines when copying the
> > header lines to whiteclnt, whitelist, or whitecommon files.
> And replace the `\n\t' with a single space, I presume.

or with 39 spaces; whitespace is ignored when for DCC header checksums.

> That certainly could be a problem.  As I was sending the original
> message, I realized the envelope recipients could be multiples too,
> and that DCC handles them somehow. 

SMTP envelope Mail_From values are not SMTP headers, and multiple
recipients must be handled.  Most SMTP headers make no sense
when not singular.  Consider Subject, From, Reply-To, and Message-ID.
I see that RFC 5451 says Authentication-Results is a "trace" field,
but RFC 5321 and RFC 5322 mention only Received fields as those that
can appear more than once.

> > I would modify your DKIM milter to generate a different header for one
> > of them, such as X-Authentication-Results-2.

> RFC5451.  I suppose I could modify the code to generate a different
> header for Domainkeys, but I'd only do that as an interim measure.
> > Or fix the milter to pick one answer instead of equivocating.  In other
> > words, generate only one Authentication-Results header.
> That would be another interim modification.

Why only a temporary change?  Why would you ever need to switch away
from X- or only generating single headers?

>     http://www.dkim-reputation.org

After looking at those web pages,
I'll spare you the rant just say that I'm unconvinced.

Vernon Schryver    vjs@rhyolite.com

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