This is stupid,
you send the email to the list, end of story, it reaches it’s destination.
the list server, should now send out the message to those in the list, using its own DMARC, DKIM, SPF.
it’s like they want spam to be legit, for the grace of GOD, drop this ARC stuff.
what this is, it’s allowing someone to modify your message, and pass it on as you.
We need to get to a point where we all have, DMARC=reject & SPF= -all, and if the message does not come with DKIM, reject it.