[dmarc-discuss] Forwarding Calendar Invitations

[Steve Atkins]

> On Aug 11, 2017, at 5:31 AM, Sim via dmarc-discuss <dmarc-discuss at dmarc.org> wrote:
> 
> Hi List,
> 
> Person A sends an invite to person B, who forwards it to person C.
> 
> If A's domain is on "reject" (or "quarantine"), B's MUA doesn't replace
> the original "From:" and C's MTA checks for DMARC, this breaks - well,
> works as designed. 
> 
> Outlook keeps the original "From" and this explains why sporadically, I
> see our domains used by our partner's MTAs.
> 
> Do you know of any other MUAs causing this kind of trouble (G-Calendar &
> Lightning doesn't)? Any remediation possible? Or just accept to have
> smaller meetings?

It's working as designed. Person A's domain owners do not want anyone
to use that domain for normal, general purpose email.

Either person A needs to stop doing that, person A's domain owners need
to stop doing that or whoever configured the mailserver for domain C
needs to modify it to take account of person A's domain owners having
internally inconsistent policies.

B's MUA could mitigate the damage by rewriting the From: field, but that will
harm everyone's email experience, whether they were on domains affected by
DMARC or not. That's not uncommon practice for mailing lists and some
sorts of forwarding at the moment (though that change may be rolled back
if ARC works to mitigate the DMARC damage in those scenarios).

Cheers,
 Steve