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:
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_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
Thread-Topic: Test Message
Accept-Language: en-US, en-AU
acceptlanguage: en-US, en-AU
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 ##