[Mailman-Users] options for dealing with DMARC

Jordan Brown mailman at jordan.maileater.net
Thu Dec 28 15:28:52 EST 2017

[ Today is not my day for getting details right.  Sigh. ]

On 12/28/2017 11:57 AM, Jordan Brown wrote:
> I've been running my mailing list for a few years with "Munge From" to
> defend against DMARC rejection.  This means that my messages get
>     From: Joe User <mymailinglist at mydomain.com>

That should be

    From: Joe User via MyMailingList <mymailinglist at mydomain.com>

>     Reply-To: Joe User <joe at example.com>
> That mostly works, but sometimes confuses people a bit, and just now
> I've had somebody send what I think was intended as a private address to

Should be "... intended as a private message to ..."

> that From line, not to the Reply-To line.  (I think their e-mail client,
> Pegasus, has an excessively flexible policy on which headers to use for
> a reply and may be subtly misconfigured, but maybe they just naively
> copied the From line.)
> That's leading me to wonder whether there's another way, whether I can
> leave From alone and still get past the DMARC checks.  Wikipedia tells
> me that DMARC passes if either SPF *or* DKIM passes.  There's no hope
> for SPF with the original sender in From, because the mailing list
> server isn't the user's mail server.  However, DKIM seems like it
> *might* pass, if I'm careful in how I configure the mailing list.  In
> particular, it looks like I'd have to get rid of the message footer. 
> That would be OK.  Looks like I might also have to kill off the
> [ListName] addition to the Subject, which is less OK but might be better
> than the alternative.
> Before I go recruit a couple of users from several DMARC-using providers
> and run some tests, can anybody tell me if there is any hope there, and
> maybe share some configuration tips?

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