My Exchange 2007 server will not send email to a certain domain. Their email address is user@endgames.us. The message I get is below. Is this problem on my end or the user's. We use Reflexions Spam Filtering and as far we are not on any blacklist. Any help will be fgreatly appreciated. Thanks. Delivery has failed to these recipients or distribution lists: John SmithYour 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: gate28.gate.iad.mlsrvr.com. _____ Sent by Microsoft Exchange Server 2007 Diagnostic information for administrators: Generating server: MailServer.mspx.com user@endgames.usgate28.gate.iad.mlsrvr.com #554 5.7.1 <user@visko-usa.com>: Sender address rejected: ACL mx_access mail server in RFC 1918 private network ## Original message headers: Received: from MailServer.mspx.com ([fe80::219:b9ff:fece:814f]) by MailServer.mspx.com([fe80::219:b9ff:fece:814f%5]) with mapi; Mon, 17 Aug 2009 12:08:55 -0400From: user@visko-usa.comTo: user@edgames.usDate: Mon, 17 Aug 2009 12:08:54 -0400Subject: TestThread-Topic: TestThread-Index: AcofVb9rSuKmz2OTQfmnAE4gEKnXDg==Message-ID: <5CF82F642F3A364E9016B8DB413B6D24BAD127C155@MSPX12.mspx.com>Accept-Language: en-USContent-Language: en-USX-MS-Has-Attach:X-MS-TNEF-Correlator:acceptlanguage: en-USContent-Type: multipart/alternative; boundary="_000_5CF82F642F3A364E9016B8DB413B6D24BAD127C155MSPX12mspxcom_"MIME-Version: 1.0

"Sender address rejected: ACL mx_access mail server in RFC 1918 private network ##" Received: from MailServer.mspx.com ([fe80::219:b9ff:fece:814f]) by MailServer.mspx.com([fe80::219:b9ff:fece:814f%5]) with mapi; Mon, 17 Aug 2009 12:08:55 -0400That's what its failing on. The receiving server is seeing your private non-routable ip address when your server connects to it.

So what must I do to correct this?

Well, it looks like its transmitting the IPV6 address in that header.Are using a firewall and NAT-ing the sending ip address of the internal server to something routable on the internet?

Hi,Please checkyour MX record.We need to verify if we have MX record pointed to the internal IP address .If yes,then please remove the internal IP address from the public DNS.We can use NSloolup to check the MX record.Using NSlookup.exehttp://support.microsoft.com/kb/200525More information to share with you: Private network http://en.wikipedia.org/wiki/Private_network 172.16.0.0/12 reject mail server in RFC 1918 private network 10.0.0.0/8 reject mail server in RFC 1918 private network192.168.0.0/16 reject mail server in RFC 1918 private network Regards, Xiu

I got the same error. It's a DNS problem. Yeah I know but how can I change the IP? Topology server.mydomain.com = 192.168.0.10 >< My router it's on 192.168.0.1 All DNS record are fine, but mx record point to server.mydomin.com that point to private network, I can't change the mx record to point to another A record, and I cant change the ip of my server LOL. How should I resolve this problem?