Re: [Qemu-devel] qemu-devel mailing list vs DMARC and microsoft.com's p=reject policy

[Thomas Huth]

On 29.03.2017 08:46, Markus Armbruster wrote:
> "Michael S. Tsirkin" <address@hidden> writes:
> 
>> On Tue, Mar 28, 2017 at 06:35:55PM +0100, Peter Maydell wrote:
>>> Hi; it's been pointed out to me that we have a problem with qemu-devel
>>> unsubscribing people because of DMARC. Specifically:
>>>  * microsoft.com publishes a DMARC policy that has p=reject
>>>  * some subscribers use mail systems that honour this and send bounces
>>>    for non-verifying emails from those domains
>>>  * the mailing list software (mailman) modifies emails that pass through
>>>    it, among other things adding the "[qemu-devel]" subject tag, in
>>>    a way that means that signatures no longer verify
>>>  * bounces back to mailman as a result of mailing list postings from
>>>    microsoft.com people can then cause people to be unintentionally
>>>    unsubscribed
>>>
>>> This is kind of painful. https://wiki.list.org/DEV/DMARC has the
>>> Mailman wiki information on the subject. In an ideal world nobody
>>> would use p=reject because it breaks mailing lists. In the actual
>>> world we have a few choices:
>>>
>>>  (1) I could set dmarc_moderation_action=Reject
>>>    * this means nobody can subscribe if they've set their dmarc policy
>>>      to reject (the "if you don't believe in mailing lists we don't
>>>      believe in you" policy).
>>>    * there is a certain purity to this option, in that it is pushing
>>>      the costs of this unhelpful mail config back on the organisations
>>>      which have chosen it; on the other hand I'm reluctant to make
>>>      life harder for people who are contributing to the project
>>>      and who typically don't have much say over corporate email config.
>>>  (2) I could reconfigure mailman to try to not rewrite anything that
>>>      we think is likely to be signed (in particular not the body or the
>>>      subject)
>>>    * this means dropping the [qemu-devel] tag from the subject, which I'm
>>>      a bit reluctant to do (it seems likely at least some readers are
>>>      filtering on it, and personally I quite like it)
>>>    * if anybody DKIM-signs the Sender: header we're stuck anyway
>>
>> For the record I'd strongly prefer this option - I tag all list mail
>> and so "qemu-devel" appears twice: in subject and as a tag.
>> Also, if mail is copied to another list, qemu-devel will
>> still appear as gmail de-duplicates email by msg id.
>> I can remove tags I don't care about but can't remove
>> subject prefixes.
> 
> Seconded.  Mailing lists messing with the subject to "help" users with
> filtering just complicate it.
> 
> Filtering on List-Id isn't any harder, and has the added advantage that
> it actually works.

The problem is that some mail clients are rather limited and you can
only filter via title there - so I guess some people would complain we
removed the tag from the subject.

Apart from that, I've also seen mailman messing up white spaces in the
body of e-mails, so this likely would only solve parts of this problem.

 Thomas