I had the same problemon Monday. The cause was that the recipients email server was seeing the private IP address of my mail server. I disabled all of the private IP addresses on my servers and then then we were able to send emails to them. Now today is Wednesday and now I get this message: 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: gate23.gate.iad.mlsrvr.com. _____ Sent by Microsoft Exchange Server 2007 Diagnostic information for administrators: Generating server: Mailserver.mspx.com user@endgames.usgate23.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::1]) by MailServer.mspx.com ([fe80::1%1])with mapi; Wed, 19 Aug 2009 11:28:12 -0400From: Joseph Burnett <user@visko-usa.com>To: John Farrell <user@edgames.us>Date: Wed, 19 Aug 2009 11:28:12 -0400Subject: Test EmailThread-Topic: Test EmailThread-Index: Acog4kRsFtdX7IGLSNyflV38+WfRjg==Message-ID: <5CF82F642F3A364E9016B8DB413B6D24BADF9420B6@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_5CF82F642F3A364E9016B8DB413B6D24BADF9420B6MSPX12mspxcom_"MIME-Version: 1.0Any help would be greatly appreciated. Thanks.

Hi,How is mail flow in your ORG , Do you placed EDGE server at front or using HUB server.Anil

Hi,Do you have proper PTR host record created for you domain.A PTR record (sometimes called a "host PTR record") is what lets someone do a "reverse" DNS lookup - that is, they have your IP address and want to know what your host/domain health.You can use below link for dns query:http://www.dnsstuff.com/http://www.checkdns.net/Also you can use below link for check whether your domain is blacklisted.http://whatismyipaddress.com/staticpages/index.php/is-my-ip-address-blacklisted?gclid=CMu5x7fWn5wCFcEtpAodH00jegAnil

NDR error: 554 5.7.1 ... Sender address rejected: ACL mx_access mail server in RFC 1918 private network This seems to indicate a problem with the MX Records, please check if the MX records are pointed to private IP addresses. We need to remove any references to private IP Addresses from the public DNS records, specifically the MX records I tried to check your MX record: visko-usa.com MX preference = 10, mail exchanger = asp-6.reflexion.net asp-6.reflexion.net internet address = 205.237.99.181 Please make sure that 205.237.99.181 is the public IP address of your mail server

hi,agree with James-Luo..please check your mx records form http://www.mxtoolbox.com/regards,Mumin CICEK | Exchange - MVP | www.cozumpark.com | www.mumincicek.com

Thanks Mumin CICEK, and James-Luo. I guess it was a hiccup in my system because now we can email this address.