Re: Google Gmail mailing list bounces

[<tomas@tuxteam.de>]

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On Fri, May 24, 2019 at 07:36:37AM +0200, Emanuel Berg via help-gnu-emacs wrote:
> Bob Proulx wrote:
> 
> >   $ dig _dmarc.zoho.eu txt +short
> >   "v=DMARC1; p=reject; sp=reject; fo=0;
> > rua=mailto:dmarc.reports.eu@zoho.eu;
> > ruf=mailto:dmarc.reports.eu@zoho.eu"
> 
> Afer figuring out this command, which wasn't
> easy [1], I get two different replies from
> executing it. This is by far the most common
> one:

[...]

>     ;; Received 122 B
>     ;; Time 2019-05-24 07:27:26 CEST
>     ;; From 192.168.10.1@53(UDP) in 1.0 ms
> 
> 
> But once, one time, after several invocations I got this:

[...]

>     ;; AUTHORITY SECTION:
>     eu.                 	600	IN	SOA	nl.dns.eu. tech.eurid.eu. 1053404310 3600 1800 3600000 600
> 
>     ;; Received 176 B
>     ;; Time 2019-05-24 07:25:22 CEST
>     ;; From 192.168.10.1@53(UDP) in 28.0 ms
> 
> 
> Questions:
> 
>     Why does one get two different replies?

Because the second one has no "DNS authority section" [1]. As a background:
this DMARC (and DKIM and SPF) stuff uses DNS as a distributed database.

Your computer is set up to ask your local domain name server (192.168.10.1).
This one asks another server, and so on, until that recursion hits the server
which "knows" where dmarc.zoho.eu is.

But your local server isn't totally stupid and keeps (caches) that answer,
because it knows you and expects you to ask again: then it can answer
right away. But because he (she?)'s a truthful server, it will tell you:
"so-and-so told me" -- that's the authority section (I don't quite remember
whether dig shows you the authority section for cached answers or for fresh
ones).

Or something like that :-)

>     What does 122 B and 176 B mean?

That would mean bytes, I think. The size of the answer.

>     What does the authority section mean?

See above.

>     Where can you see their mailing list policy?

That should be the very first line of the DNS reply:

> v=DMARC1; p=reject; sp=reject; fo=0; rua=mailto:dmarc.reports.eu@zoho.eu; ruf=mailto:dmarc.reports.eu@zoho.eu

(I can't say in detail what each of those things means, but there's quite
a bit of docs on that around)

That all said... I'd urge everyone to chose a mail provider who
cares about mail. The big ones, the "free" offers and your ISP
all want to kill mail because there's no money in it.

Since they can't kill it directly, they starve it. Spam (and
the corresponding anti-spam measures) are their allies in that.

There are small mail providers who take a very affordable amount
(here in DE typically 1EUR/month) and actually know what they
are doing (e.g. posteo.de, mailbox.org). Consider supporting
those.

Cheers

[1] https://en.wikipedia.org/wiki/Domain_Name_System#Authoritative_name_server
-- tomás

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