-----Original Message-----
From: ietf-dkim-bounces(_at_)mipassoc(_dot_)org
[mailto:ietf-dkim-bounces(_at_)mipassoc(_dot_)org] On Behalf Of Ian Eiloart
Sent: Thursday, May 19, 2011 3:21 AM
To: John Levine
Cc: <ietf-dkim(_at_)mipassoc(_dot_)org>
Subject: Re: [ietf-dkim] New canonicalizations
Probably true, but if the difference between 10% broken and 8% broken
signatures is independent of whether the email is spam, then actually
"relaxed" seems to be producing a 20% reduction in signature breakage.
I'd argue that a 20% reduction in broken signatures *is* actually "much
better".
That statistic is largely meaningless unless there's a basis for comparison.
For example, it would be useful to observe that the same message, sent with
each of the four canonicalizations, to the same set of destinations using the
same endpoint software, produced different results given that one changing
variable. But if domain X only ever tried sending with relaxed/relaxed and
generally gets good results, there's nothing in that datum to say that
simple/simple would not have worked just as well for the same sender with the
same mail. Thus I don't believe there's enough data to support your conclusion.
That relaxed/relaxed appears to survive 20% more might be based on the fact
that the people using it send clean mail through clean paths, and it's as
simple as that.
To determine that, we'd need a pareto analysis of breakage modes.
Presumably lists that aren't re-signing are responsible for some of
this, as are broken signing mechanisms. The questions remaining are,
"is there anything left after excluding those two cases?", and "how
much of that could be fixed easily?".
Our stats are unable to tell what the problem is in all cases, but for mail
we've received where the signer used the "z=" tag, the biggest signature
breaker in terms of header changes is modified To: fields. I suspect that's
either rewriting by lists to add the list description as a comment, or
improperly quoted comment fields that are corrected along the way.
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