Except that this is not applicable. In my case my mailserver is not hosted at Swisscom but on my own infrastructure, is on the same IP since years, has proper MX records and reverse DNS entries and has delivered email to the same bluewin customer yesterday successfully. Only the reply on that receiver today which I received and replied again got rejected. And the response is cryptic to me.  

And if you mail to abuse@bluewin.ch you get the same error...

So who is this famous DNSNULL I should contact?



On 11 Jul 2019, at 13:49, Florin sfetea <f_sfetea@yahoo.com> wrote:

 
 
Beste Grüsse, Regards si s-auzim de bine 
Florin Sfetea
 
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Subject: swinog Digest, Vol 174, Issue 3
 
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Date: Thu, 11 Jul 2019 11:32:38 +0200
From: Andreas Fink <afink@list.fink.org>
Subject: [swinog] bluewin & DNSNULL
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Does any one have a clue what DNSNULL means in the following context of a mail delivery error?
 
 
 
dzmsp-mxin12.bluewin.ch <http://dzmsp-mxin12.bluewin.ch/> Swisscom AG IP: 79.134.251.203, You are not allowed 
to send us mail. Please see DNSNULL if you feel this is in error)Reporting-MTA: dns; mail.fink.org <http://mail.fink.org/>
Arrival-Date: Thu, 11 Jul 2019 11:19:58 +0200
...
 
 
 
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