Forwarding alone shouldn't be blowing up messages. If you're doing
something to the message content that invalidates the DKIM signature
or causes the the from address and return path to not be aligned,
that's where you're going to run into problems. If you don't modify
the message in any way while forwarding it on, you shouldn't run
into issues due to DMARC.
The above first sentence is a widely held view, using typical language.
However the sentence is wrong in so many different technical and
operations ways and levels, that it mostly services as an example of the
problem in talking about email. At base, it relies on a simplistic
model that produces Procrustean assertions. At base, it's just wrong.
Mailing lists take delivery of a message and posts a new one. Most
mailing lists get their utility by facilitating communication between
original authors and final recipients. Mailing lists vary in the value
add they provide in this process; it often includes modifying the
original message in a variety of entirely legal -- and often useful --
ways.
Again, what they do is legal and useful, and has been for 30 years.
Any assertion or implication that a mailing list, which re-posts a
legitimately and usefully modified message, is somehow doing something
wrong, is itself the problem.
The mailing list is not the problem. The problem is over-application of
mechanisms or policies that render legitimate email non-functional.
There are serious email abuses motivating the over-application. They
shouldn't be ignored. However, the fact of those abuses are serving to
create new ones. Calling the new problems are abuses sounds impolitic,
but how else should breaking long-standing, independent, legitimate
email service be characterized?
It's entirely possible that the work-arounds being pursued, with new
modifications to rfc5322.From and rfc5322.Reply-To will suffice. But
they carry their own downsides.
On the average, a hack to remedy a hack damages the system and often
requires more hacks.
Architectures usually layer nicely. Hacks rarely do.
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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