Hi,
A completely different question: Is there anyone that has a working non-naive setup for ARC signing of mail list mail in mailman? I've tried both the built-in version but it was not usable in the version I tried for the case where there are several domains with different selectors and keys and where the outgoing mail also is DKIM-signed. This might be that the documentation is lacking but a very shallow look in the source gave me the impression that the implementation is limited to one domain which is not enough for my use case as I have lists in several domains.
I use DKIM on outgoing mail with a setup where each domain has its own keys and selectors. As discussed here earlier, the DKIM signature should be added before the ARC signature. I have tried to use rspamd after a tip here for this but without luck so far, but this is somewhat off topic for mailman although related of course. rspamd seems very good for other purposes and solves my other problems with greylisting, DKIM-signing and spam filtering. That said, ARC seems difficult to get to work for forwarded mails there also...
cheers // David