A bit off-topic: problems with sending to a Gmail user

[Joerg Dorchain]

On Sat, Mar 12, 2022 at 09:03:37AM +0100, Matthias Apitz wrote:
> 
> > > I've been seeing a lot of that lately.  Google seem to have tightened
> > > their email security practice recently.
> > > 
> > > It appears that 1blu is doing something that GMail doesn't like.  They
> > > probably have a number of users who have the same problem.  I would
> > > ask them to check their MTA configuration against the section "Make
> > > sure your messages are authenticated" in the referenced page
> > > (https://support.google.com/mail/answer/81126#authentication).
> > > 
> > > >     550-5.7.26 This message does not have authentication information or fails to
> > > >     550-5.7.26 pass authentication checks. To best protect our users from spam, the
> > > >     550-5.7.26 message has been blocked. Please visit
> > 
> > Authenticated in this context means, you don't have SPF / DKIM / DMARC set up.
> > 
> > You can use this service: https://www.mail-tester.com to test your
> > setup. It provices you an email address. Send an email to it
> > and then your mail and server setup will be evaluated.
> 
> Thank you, Stefan.
> 
> I did such a test and the result can be seen here: 
> https://www.mail-tester.com/test-ahwup3i9z

Let's go through that:

- An SPF-entry has to be created in the unixarea.de domain, I would assume you can do that via the
  interface of 1blu.de

- DKIM-headers can be inserted locally. If you do that with a selector under the unixarea.de domain, you
  have to add the corresponding key in the zone. I would assume you can do that via the interface of 1blu.de
  Alternatively dkim can be implemented at the 1blu.de MTA, which in turn is solely at their discretion.

- Same for a DMARC-entry.

This would make most sense when you enable DNSSEC for the unixarea.de domain.  Check here:
https://dnsviz.net/d/unixarea.de/dnssec/ I would assume you can do that via the interface of 1blu.de.

Bye,

Joerg
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