Exchange 2007 Delivery Failures reported because MX-PRIVATE

We recently migrated to Exchange 2007 inc. SP1 and all of our mail being sent externally is working except when I sent to two specific external users at different companies. We immediately get an Undeliverable message as shown below.

Our Exchange server is a single server handling Hub, Client, and Mailbox roles located on our internal network with a Private IP address, running on a Windows Server 2008 x64 platform. There is an Internal DNS server and a DNS server located at our ISP. Externally, our mail server and MX records all point to the public IP of our firewall appliance. Internally, DNS has a private IP for our Exchange server and MX record.

IPv6 is disabled on the Exchange Server and Client PC.

Any assistance with this would be appreciated.

Delivery has failed to these recipients or distribution lists:
 
'RECEIVER_EMAIL_ADDRESS'
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.
 
The following organization rejected your message: RECEIVER_FQDN_SERVER.
 
  _____  
 
Sent by Microsoft Exchange Server 2007 
 
 
 
 
 
 
 
Diagnostic information for administrators:
 
Generating server: OUR_FQDN_SERVER
 
RECEIVER_EMAIL_ADDRESS
RECEIVER_FQDN_SERVER #554 5.7.1 <MY_EMAIL_ADDRESS>: Sender address rejected: UBE-SENDER MX-PRIVATE Your MX record is in RFC 1918 private network ##
 
Original message headers:
 
Received: from OUR_FQDN_SERVER ([::1]) by
 OUR_FQDN_SERVER ([fe80::24f6:417e:ac6a:381%15]) with mapi; Mon,
 27 Oct 2008 14:33:52 +1000
From: "MY_NAME" <MY_EMAIL_ADDRESS>
To: "'RECEIVER_NAME'" <RECEIVER_EMAIL_ADDRESS>
Date: Mon, 27 Oct 2008 14:33:51 +1000
Subject: a
Thread-Topic: Test Message
Thread-Index: Ack37O7XfG/X5q65QVCzz84eTGX7Kw==
Message-ID: <05F333E6DE387A40937EB59DBBCCCC751DE278A6E9@OUR_FQDN_SERVER>
Accept-Language: en-US, en-AU
Content-Language: en-US
X-MS-Has-Attach: yes
X-MS-TNEF-Correlator:
acceptlanguage: en-US, en-AU
Content-Type: multipart/related;
	boundary="_006_05F333E6DE387A40937EB59DBBCCCC751DE278A6E9_";
	type="multipart/alternative"
MIME-Version: 1.0
 
 
------------------------------------------------------------------------
 
The other rejection message received is
 
 
 
RECEIVER_FQDN_SERVER #554 5.7.1 <MY_EMAIL_ADDRESS>: Sender address rejected: ACL mx_access mail server in RFC 1918 private network ##

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commvisiAsked:
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tenaj-207Commented:
The first I'd check is the Recipient Filtering.  It's found in the Exchange Management Console under the Organization Configuration then Hub Transport.  Under there is a tab called Anti-Spam.  Click on that tab and right click on Recipient Filtering, check here to confirm that they aren't in the blocked list.  Someone may have accidentally put them in this list thinking it would white list them.
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commvisiAuthor Commented:
Thanks for the comment. I do not have an Anti-Spam tab under Organization Config/Hub Transport.

Also, The problem doesn't seem to be specific to an individual in the orginisation as I receive the same Undeliverable message if I sent to any person in that orginisation.

Thanks.
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tenaj-207Commented:
Well.. I guess that's not the issue.  If you wanted to install it then you would follow these steps.
http://support.microsoft.com/kb/555924

However, seeing as that must not be the issue check the event logs and run the Mail Flow Troubleshooter, found under Toolbox in the EMC.  Post anything or interest.

Also ping the problem company mail servers and then use mxtoolbox.com to make sure the IP addresses match up.
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tenaj-207Commented:
Commvisi,

I'm glad to see that your problem was resolved, however I'm concerned that their might still be an issue considereing the bad grade you gave the solution.  Can you please explain why you choose to grade the answer as you did?  Or if there is still something wrong we can continue to work on the issue.

Thanks,
Jeff
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modus_operandiCommented:
Grade changed to 'A'
 
modus_operandi
EE Moderator
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