My company users unable to send emails to some of the domains. Please I need help for the following error: Delivery has failed to these recipients or distribution lists: tamer@optima.tc An error occurred while trying to deliver this message to the recipient's e-mail address. Microsoft Exchange will not try to redeliver this message for you. Please try resending this message, or provide the following diagnostic text to your system administrator. The following organization rejected your message: natrohost.com. _____ Sent by Microsoft Exchange Server 2007 Diagnostic information for administrators: Generating server: eccmail.etesal.com.sa tamer@optima.tc natrohost.com #554 This server requires PTR for unauthenticated connections. ## Original message headers: Received: from eccmail.etesal.com.sa ([192.168.0.7]) by eccmail.etesal.com.sa ([192.168.0.7]) with mapi; Wed, 13 Jul 2011 15:18:38 +0300 From: "Asrar M. Khan" <asrar@etesal.com.sa> To: "tamer@optima.tc" <tamer@optima.tc> CC: Mohammad Shahadeh <mohammad@etesal.com.sa> Disposition-Notification-To: "Asrar M. Khan" <asrar@etesal.com.sa> Return-Receipt-To: <asrar@etesal.com.sa> Date: Wed, 13 Jul 2011 15:18:35 +0300 Subject: Questions re Installation Thread-Topic: Questions re Installation Thread-Index: AcxBVvzLwX8DV3nNRpWzzZCUV5Vd9Q== Message-ID: <AED830FC6D203C478659B9817CFD0ADB01657EBBAE74@eccmail.etesal.com.sa> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/related; boundary="_004_AED830FC6D203C478659B9817CFD0ADB01657EBBAE74eccmailetes_"; type="multipart/alternative" MIME-Version: 1.0

What you need to do is setup a PTR record for your sending mail server. Set one up. - http://support.microsoft.com/kb/300171 Sukh