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Lets say we have 2 domains, and Both point to the same MX records with the same priority, and, both of which send the mail through our ISP's filtering/scanning service. From there, mail for both domains is delivered to our on-premises Exchange server using SMTP. In other words, the routing for messages sent to both domains is exactly the same.

  • We are seeing consistent failed delivery of messages sent from Gmail to, but only for some Gmail users. For some Gmail users, messages are consistently delivered to
  • On the other hand, messages sent to are delivered consistently, even when sent by Gmail users whose mail is failing to

A bounce message for messages sent to looks like this:

Delivery to the following recipient failed permanently:

Technical details of permanent failure:=20
Google tried to deliver your message, but it was rejected by the recipient =
domain. We recommend contacting the other email provider for further inform=
ation about the cause of this error. The error that the other server return=
ed was: 571 571 Server listed in SpamCop RBL (state 14).

----- Original message -----

Received: by with SMTP id a1mr18153847obw.32.1326873881149; We=
 18 Jan 2012 00:04:41 -0800 (PST)
MIME-Version: 1.0
Received: by with HTTP; Wed, 18 Jan 2012 00:04:00 -0800 (PST)
X-Originating-IP: []
From: Graeme Donaldson <graeme@bla.bla>
Date: Wed, 18 Jan 2012 10:04:00 +0200
Message-ID: <CAOBQ9=3Dmx674mUAw1E6_gED11rWzwnFUzWBaKpWLVE_xB8-tGjg@mail.gma=>
Subject: test
Content-Type: text/plain; charset=3DISO-8859-1

By contrast, the SMTP headers from a successfully delivered email look like this:

Received: from (196.x.y.z) by
 (172.x.y.z) with Microsoft SMTP Server id 14.1.323.3; Wed, 18 Jan 2012
 10:23:23 +0200
Received: from (Not Verified[]) by with MailMarshal (v6,8,4,9558)   id <B4f16817a0000>; Wed,
 18 Jan 2012 10:23:22 +0200
Received: by qcsp14 with SMTP id p14so2850129qcs.34        for
 <>; Wed, 18 Jan 2012 00:23:21 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=gamma;
MIME-Version: 1.0
Received: by with SMTP id b27mr8321239qck.124.1326875001168; Wed,
 18 Jan 2012 00:23:21 -0800 (PST)
Received: by with HTTP; Wed, 18 Jan 2012 00:23:21 -0800 (PST)
Date: Wed, 18 Jan 2012 10:23:21 +0200
Message-ID: <>
Subject: test
From: User <>
To: <>
Content-Type: multipart/alternative; boundary="001d605b95931b230b04b6c92924"
X-MS-Exchange-Organization-AuthAs: Anonymous

Comparing the SMTP headers, I note that there are 3 "Received:" headers that seem to be entirely within Google's network, with the 4th "Received:" header being the first time it breaks out of Google's network. Looking at the bounce message, it only has 2 "Received:" headers, which makes me think this failure is within Google's network.

Google is notoriously uncontactable for stuff like this so I'm hoping someone else has seen something similar. Has anyone had a similar issue?

share|improve this question
up vote 1 down vote accepted

Here is the relevant error message:

The error that the other server return=
ed was: 571 571 Server listed in SpamCop RBL (state 14).

One of google's outbound servers got blacklisted by SpamCop. This happens from time to time as people give their password to phishing attacks. Then attackers use google accounts, and after a few reports, one of google's servers get blacklisted.

You may consider not using spamcop lists on the MX servers, if they are under your control.

share|improve this answer
Unfortunately I don't control the MXs, but the issue did stop as abruptly as it started so its probably this. – ThatGraemeGuy Feb 21 '12 at 12:21

SpamCop will automatically blacklist a server if a certain number of users report the server (IP) as a spamming server. Once the reports stop, the server is automatically removed from the blacklist.

Google obviously has more than one SMTP server, each with their own DNS cache. It is possible that the one server cached the blacklist result.

share|improve this answer
This is plausible. This issue stopped just as abruptly as it started without us or the ISP changing anything. – ThatGraemeGuy Feb 21 '12 at 12:20

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