[BBLISA] DMARC issue, Yahoo and beyond

[Brian O'Neill]

IIRC, the issue is not with the From: and Reply-To: headers, but the 
envelope sender (MAIL FROM in the SMTP chatter).

Some systems, especially mailing lists, when forwarding on behalf of the 
original sender, don't reset the envelope sender to the local domain, 
and use the original sender's email address. You then bump into problems 
if the receiving host is checking SPF and DKIM (DMARC is basically 
both), and the original sender's domain has those set and have strict 
checking.

We ran into this when a person had their email forwarded to a yahoo 
account from an Exchange 2003 server. Exchange 2003 doesn't change the 
envelope sender on forwarding, but I understand that 2007 and later 
change the envelope sender to be the forwarding account.

I haven't looked any deeper yet at my mailman stuff, as fortunately I 
don't have any yahoo recipients or any other domain that is doing DMARC yet.

On 5/15/2014 10:15 AM, Edward Ned Harvey (bblisa4) wrote:
> Before anybody says "Don't use yahoo," this is both a reasonable thing for yahoo to do, and something that others can and should and will (like it or not) be adopting more in the future.
>
> Apparently yahoo recently set their DMARC policy to reject, which means yahoo users can't participate in mailing lists such as this one.
>
> Anybody here using yahoo?  Try posting to the list, and prove or deny, that you can't?
>
> Here is the official mailman page on the subject:
> http://wiki.list.org/display/DEV/DMARC
>
> It seems, the solution is to enable "from_is_list" so the message will actually send "From: Edward Ned Harvey via The List" and "Reply-To: Edward Ned Harvey <myemail at nedharvey.com>"
>
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