A competent mailing list admin would reject all messages from
dubious sources. But it would be foolish to assume that all such
admins are as competent as we would wish. So the mere fact that they
(re)sign messages does not prove their origin, except insofar as you
are prepared to have confidence in their competence.
I've been subscribing to mailing lists since the 1970s, and other than
a brief flurry about 15 years ago when spammers used open lists as
mail amplifiers, I have never seen bad mail leaking through lists as a
particularly serious or insoluble problem.
Could you explain why you think DKIM will make hitherto competent list
managers unable to control what gets onto the lists, and perhaps
suggest a few lists where you expect the managers to be too
incompetent to manage what gets onto the list, yet competent enough to
add DKIM verification, add an A-R header, and resign it?
R's,
John
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