> On May 3, 2022, at 9:30 AM, John R. Hogerhuis <[email protected]> wrote:
> If anyone has a suggestion that I can try in Mailman I'll try it.

Hi John,

In my own opinion the safest thing to do is to sigh and implement one of 
mailman's two header munging policies:

Option A is:
set dmarc_mitigate_action to munge_from
set (if not already enabled, it appears to be) reply_goes_to_list
net result: mailman will look up the submitter's DMARC record, and if 
policy=quarantine or policy=reject is set, munge the header; messages will look 
a little different if submitted by one of those users.

Option B is:
set dmarc_mitigate_action to munge_from
set dmarc_mitigate_unconditionally
set reply_goes_to_list
net result: mailman will always munge From: regardless of the submitter's ESP 
policy; messages will look a little different.

Option C -- leaving well enough alone -- should be on the table as well, for a 
variety of reasons.

Note also that I haven't run a mailman of my own for over a decade, well before 
the publication of RFC7489.  The suggested configurations are based on doc 
reading and applying the lessons of running (non-mailman) mail systems at work 
that deliver a million messages a day.

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