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

[raf]

On Sat, Mar 12, 2022 at 09:03:37AM +0100, Matthias Apitz <guru at unixarea.de> wrote:

> El día viernes, marzo 11, 2022 a las 03:12:41p. m. +0100, Stefan Hagen escribió:
> 
> > > 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
> 
> > This is an example from me:
> > https://www.mail-tester.com/test-3ghr082f2
> > 
> > Feel free to examine it and set your host up in a similiar way.
> 
> As far as I understand all the changes can't be done on my host (a
> laptop). I send mails with mutt and mutt with sendmail to smtp.1blu.de
> 
> And I'm afraid, if I contact the support of 1blu I don't know if they will
> react (I've mixed experience from the past). I will give it a try...
> 
> Thanks
> 
> 	matthias
> 
> -- 
> Matthias Apitz, ✉ guru at unixarea.de, http://www.unixarea.de/ +49-176-38902045
> Public GnuPG key: http://www.unixarea.de/key.pub

So it looks like the real problem might be "You're
listed in 1 blacklist" (http://www.backscatterer.org).
Try to get removed from it. Good luck. It sounds like
the mail server you are using needs a configuration
change to stop backscatter. Perhaps you could direct
your mail server providers to that site.

cheers,
raf