[exim] [OT] CNAME in PTR record is invalid?

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Author: Heiko Schlittermann
Date:  
To: Exim Mailing List
New-Topics: [exim] Update: problem gets resolved : Re: [OT] CNAME in PTR record is invalid?
Subject: [exim] [OT] CNAME in PTR record is invalid?
Hello,

I know, it's not strictly relevant to Exim, but I know that here a some
experienced postmasters … and I hope, some of you may even have
connections to 1und1, web.de or some of these companies…

Since about yesterday we experience a strange behaviour of big German
hosters (I believe, they all are part of the United Internet company):

They refuse to accept mails from our systems:

    SMTP error from remote mail server after initial connection:
    host mx01.kundenserver.de [212.227.17.191]: 554-kundenserver.de (mxeue006) Nemesis ESMTP Service not available
    554-No SMTP service
    554 invalid DNS PTR resource record, IP=212.80.235.156



But "dig -x 212.80.235.156" is (according to RFC2317)

    ;; ANSWER SECTION:
    156.235.80.212.in-addr.arpa. 86265 IN       CNAME   156.128-191.235.80.212.in-addr.arpa.
    156.128-191.235.80.212.in-addr.arpa. 86265 IN PTR web-server.langer-emv.de.


And even dig 'web-server.langer-emv.de' maps to the address in question:

    ;; ANSWER SECTION:
    web-server.langer-emv.de. 86400 IN  A   212.80.235.156



Is there anybody with any good idea?

    Best regards from Dresden/Germany
    Viele Grüße aus Dresden
    Heiko Schlittermann
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