DMARC is increasingly being used as a spamfilter, checking whether the sender ought to send mail via this route. To comply with this for mail sent through Mailman, we will change the From: sender address to the list address. The current:

> From: Some User <some.user@somewhere.domain> > Sender: "listname" <>

will be changed to:

> From: Some User via listname <> > Reply-To: Some User <some.user@somewhere.domain> > Sender: "listname" <>

If you filter or forward mail automatically, you might need to change the filter.