I've just added support to our majordomo for rewriting the From:
header when the sender's domain has a DMARC policy. Messages from
domains using DMARC will now have a From: header like:
From: "John Connor via misc" <misc@openbsd.org>
and the original From: address is preserved in the X-Original-From:
header if one is not already present.
This seems like the only reliable way to address the problem given
that the mailing list server often reformats or otherwise modifies
the message body.
The rewriting currently happens even for a DMARC policy of "none"
since some large senders (for example gmail.com) use a policy of
"none" but receivers may still enforce SPF. I could relax this but
I worry that doing so will lower the IP or domain "reputation" in
Google's eyes (something that is already a black box).
- todd
