Hello, I use Exhcnage 2007 and a user sends emails from an external email account to a distribution list which does not required authentication. The user told nme first that he was receiving IP has been found on the block list, tehn I asked the user to send me the email from his external email account to mine in order to check the header and see the IP used for communicating. I also did a nslookup > set type=mx > orange.fr and I added the IP as green IPs on the Edges. But the user keeps receiving email as below. I did checked the quarantine items = 0 results, same for the Spam.. I also tracked the email but could not find any track (By the way, I wonder if it means that the email did not event reach my servers..) Finaly, I had a glance at the red IPs and could not find the user's excternal IP in it. Could you please help me out and give me some clues as I start to get pretty lost. This is the mail system at host mwinf2801.orange.fr. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system <graig@company.com>: host mail3.company.com[xx.14.xxx.225] said: 550 5.7.1 Recipient not authorized, your IP has been found on a block list (in reply to RCPT TO command) <OUEST.dp.elus@comp-any.com>: host mail3.comp-any.com[xx.14.xxx.225] said: 550 5.7.1 Recipient not authorized, your IP has been found on a block list (in reply to RCPT TO command) Reporting-MTA: dns; orange.fr X-SMTP-Server-Queue-ID: 0068980005E7 X-SMTP-Server-Sender: rfc822; user@orange.fr Arrival-Date: Mon, 13 Sep 2010 20:49:08 +0200 (CEST) Final-Recipient: rfc822; graig@company.com Action: failed Status: 5.7.1 Remote-MTA: dns; mail3.company.com Diagnostic-Code: smtp; 550 5.7.1 Recipient not authorized, your IP has been found on a block list Final-Recipient: rfc822; DISTRIBIONLIST2@comp-any.com Action: failed Status: 5.7.1 Remote-MTA: dns; mail3.comp-any.com Diagnostic-Code: smtp; 550 5.7.1 Recipient not authorized, your IP has been found on a block list

Hi, 1. If the DL can receive messages from other external mail addresses? 2. If the problem only happens when sending the message to this DL? To narrow down the root, I recommend you create a new DL which does not required authentication for testing. If the user can send the message without problem, the problem should reside in the DL. Please try the following steps disable the SenderAuthentication: Open EMS, type: Set-DistributionGroup -identify DL -RequireSenderAuthenticationEnabled :$falsePlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Thanks Gen Lin-MSFT