there's an ARC addon for Mailman and we use that, the DMARC damage
should drop considerably, without us having to change the way we use our
lists.
It's not clear to me that this is true John. DMARC Validators will need to take
ARC into consideration and we don't know what adoption will look like other
than a handful of players at this point.
I certainly don't think that ARC will make all the problems go away, but
it should mostly fix the problems at Gmail and Yahoo which are a large
fraction of the mail traffic.
For smaller sites, if they do anything with DMARC at all, they'll still
need to whitelist mailing lists, which of course they could do now.
R's,
John