Dear Experts
What is the best way to go about reconciling GNU Mailman3-made message modifications (like message footers or subject prefixes) with sender-made DKIM signatures? I am aware of the "DMARC mitigations" tab in the list settings, not bad, but it looks that "replace From: with list address" doesn't help (of course), whereas wrapping the message in an outer message often looks ugly. Is there a better way?...
BTW I would like to point out that broken DKIM signature can be a problem even with an easy DMARC policy; for example ProtonMail will display this flashy red warning: https://protonmail.com/support/knowledge-base/email-has-failed-its-domains-a... in its webmail. (I guess nothing can be done about it except "DMARC Mitigate unconditionally").
This is GNU Mailman 3.1.
Thanks!