Re: [libreoffice-users] Re : Bouncing messages from users -AT- global.libreoffice.org

At 11:42 31/12/2019 +0100, M Henri Day wrote:
> Den tis 31 dec. 2019 kl 05:00 skrev <users+owner@global.libreoffice.org>:
> > Hi, this is the Mlmmj program managing the 
> > <users@global.libreoffice.org> mailing list.
> >
> > Some messages to you could not be delivered. If you're seeing this 
> > message it means things are back to normal, and it's merely for 
> > your information.
> >
> > Here is the list of the bounced messages:
> > - 55635
>
> From time to time I receive messages of the type above, but never 
> any information about what I am expected - or allowed - to do with 
> the <<list of bounced messages>> which accompanies them. Can anyone 
> on the forum enlighten me ?

At 12:54 31/12/2019 +0200, Hylton Conacher wrote:
> I also had the same message and note that it was for the same 
> message number that was "missed". As I am sure we are not using the 
> same ISP in South Africa, so who knows maybe the mailing list admins 
> picked it up as spam. ANYONE know?

I think I do.

The list help text says "Anyone can retrieve message number N from 
the list's archive by sending a message to 
<users+get-N@global.libreoffice.org> (change the N to the number
of the desired message)". But if I'm right, any repeat copy would 
also fail to be delivered to you.

It's all down, I think, to DMARC; see 
https://en.wikipedia.org/wiki/DMARC . This is a well-intentioned 
scheme to allow mail providers to reject incoming messages if they 
originate from a mail server which is not a registered server for the 
domain in the From: header. Such messages will generally be spoofed 
and thus spam, so this is a Good Thing. But a problem arises if 
mailing list processors (quite sensibly) preserve the original From: 
address on forwarded messages - as does the LibreOffice Users list 
processor. The forwarded message claims to be from the original 
sender (which it is, of course), but is injected into the LibreOffice 
mail server, which gives it the appearance of being a spoof message. 
You will fail to receive such messages if both (1) the originating 
mail domain publishes a list of approved servers and requires 
receiving systems to reject messages from elsewhere, and (2) your 
mail provider chooses to play ball and obey this requirement.

My mail domain (which is Yahoo in disguise) satisfies condition (1), 
so you will fail to receive my messages to the list if your mail 
provider satisfies condition (2). I do not receive copies of my own 
contributions. Message 55635 is, I think, my contribution to the 
thread "full date string to date"; you can see this at
http://document-foundation-mail-archive.969070.n3.nabble.com/full-date-string-to-date-td4271380.html 
. If I'm right, you will not receive copies of this message via the 
list, which is why I'm copying it to you both directly.

There are solutions to this problem, the simplest of which is for the 
list processor to append something such as ".INVALID" to the From: 
address in relevant messages, so that they are no longer recognised 
as coming from a DMARC-conformant domain. Many mailing list providers 
do this. I wrote to <postmaster@documentfoundation.org> about this as 
long ago as 1 May 2018, but my suggestion for action was rejected, on 
the ground that "none of the workarounds [are] satisfactory for 
everyone". Thus the problem continues ...

Brian Barker  


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