[Mailman-Users] Executive summary of DMARC issues
Larry Finch
finches at portadmiral.org
Thu May 15 14:47:48 CEST 2014
On May 14, 2014, at 11:47 PM, Stephen J. Turnbull <stephen at xemacs.org> wrote:
> Peter Shute writes:
>
>> When MS365 forwards the mails sent to the distribution list, should
>> that make the DMARC authentication fail? I thought that only
>> happened if you made changes like adding a prefix to the subject
>> line like Mailman does.
>
> If it forwards verbatim *and* the sending domain signs the mail with
> DKIM (the common case), DMARC validation will succeed. Without DKIM,
> DMARC validation is guaranteed to fail. However, even in the sender
> uses DKIM, *any* change *whatsoever* to the body will cause validation
> to fail, and there are several changes to the header that could cause
> it to fail. Furthermore, which parts of the header are protected by
> the DKIM signature are determined by the sender, not by DMARC AFAIK.
>
> If distribution lists are pure forwards, MS365 will be OK. But I find
> it hard to believe that that level of functionality is popular with
> users -- there's a reason why all popular MLMs implement subject
> prefixes, body headers and body footers, and it isn't "because it's
> the Microsoft way".
>
>
Especially as legally mailing lists are required to add unsubscribe instructions in the footer.
best regards,
Larry
--
Larry Finch
finches at portadmiral.org
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