For DMARC, we have been rewriting the From: header which is used by patchwork to determine the submitter of a patch. Now, the mailing list appears to be the submitter and Patchwork is sending out notifications to the list (https://lists.ipfire.org/pipermail/development/2018-February/004110.html) which is of course absolutely not intended. There is a bug in patchwork, but no solution (https://github.com/getpatchwork/patchwork/issues/64). It appears again, that it is a better solution to not let mailman rewrite anything and pass the mail through unmodified.
The mailing list has been changed back to not rewrite the From: header any more. Therefore this should be fixed.