[RFC6377] provides some guidance on using DKIM with Mailing lists.
The following mitigation techniques can be used to ease
interoperability issues with DMARC and Mailing lists:
It should probably be indicated whether these techniques would be applied
to all messages, or only to messages sent from domains with a DMARC
policy other than "p=none". (I prefer the latter.)
It's an implementation issue, depending on whether the list software
can get the DMARC policy from a DNS query or from an
Authorization-Results header. My MTA puts an A-R header on incoming
mail so I have a shim after the list manager that looks at the A-R
header and rewrites the From: address (into dmarc.fail addresses,
which some people imagine are not deliverable) if it sees a DMARC
policy.
o Configuring the MLM to "wrap" the message in a MIME message/rfc822
part and to send as the Mailing List email address. Many email
clients (as of the publication of this document), especially
mobile clients, have difficulty reading such messages and this is
not expected to change soon.
This seems like a quite elegant solution. I'm very surprised by the second
sentence - are these clients that have difficulty with many Content-Types
or is it a specific issue for message/rfc822?
It's a one-entry MIME digest, so it looks like a digest, not an
individual message.
R's,
John