Hi, I am experiencing an odd issue with one of my clients. They are getting 5.2.1 bounce backs from a particular domain ONLY when the message originates from OWA or their iPhones(sent through Exchange profile). When the e-mail is sent from Outlook (or a 3rd party e-mail provider like GMail), the e-mail gets delivered fine..but OWA and the iPhones want to believe there is a problem. Headers below: (I changed names,usernames, and IP addresses to keep the message private, all other text is left as-is. Delivery has failed to these recipients or distribution lists: Username / Company There's a problem with the recipient's mailbox. 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. Diagnostic information for administrators: Generating server: hostname.company.home.usa user@company.com #< #5.2.1> #SMTP# Original message headers: Received: from sm2.company.com ([172.18.16.4]) by hostname.company.home.usa with Microsoft SMTPSVC(6.0.3790.3959); Tue, 12 Jan 2010 08:09:20 -0500 Return-Path: <sender@originating-server.org> Received: from host.company.com ([172.18.16.61]) by company.com (sm2.company.com [127.0.0.1]) (MDaemon.PRO.v6.8.5.R) with ESMTP id 32-md50000000006.tmp for <recipient@company.com>; Tue, 12 Jan 2010 08:08:28 -0500 Received: from smtpx-filter.company.com (filter [17.1.6.9]) by fpcaix0.company.com (Postfix) with ESMTP id 993B4A5 for <recipient@company.com>; Tue, 12 Jan 2010 08:08:28 -0500 (EST) X-ASG-Debug-ID: 1263301701-63c5813f0001-e7Y8I6 Received: from remote.originating-server.org (17-1-1-4-BusName-washingtonDC.hfc.comcastbusiness.net [17.1.1.4]) by smtpx-filter.company.com with ESMTP id z2Ylwkx8vOe2jgxH; Tue, 12 Jan 2010 08:08:22 -0500 (EST) X-Barracuda-Envelope-From: sender@originating-server.org X-ASG-Whitelist: Sender Received: from I-SBS.i.local ([fe80::5aa:47eb:1560:7855]) by I-SBS.i.local ([fe80::5aa:47eb:1560:7855%11]) with mapi; Tue, 12 Jan 2010 08:08:21 -0500 Content-Type: multipart/mixed; boundary="_000_991D06FFAF8F4433B1CB52A309A2AB35originating-serverorg_" From: Sender <sender@originating-server.org> To: Recipient <recipient@company.com>, Second Recipient <Second.Recipient@company.com> Date: Tue, 12 Jan 2010 08:08:17 -0500 X-ASG-Orig-Subj: Test Subject: Test Thread-Topic: Test Thread-Index: AcqTiFAK/q6U7O8yT92TgA7v24VWuw== Message-ID: <991D06FF-AF8F-4433-B1CB-52A309A2AB35@originating-server.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: <991D06FF-AF8F-4433-B1CB-52A309A2AB35@originating-server.org> acceptlanguage: en-US x-pp-processed: __PP2__16ea268a-606b-43db-b564-3eeafdcfccaa MIME-Version: 1.0 X-Barracuda-Connect: 17-1-1-4-BusName-washingtonDC.hfc.comcastbusiness.net[17.1.1.4] X-Barracuda-Start-Time: 1263301701 X-Barracuda-URL: http://17.1.6.9:8000/cgi-mod/mark.cgi X-Virus-Scanned: by bsmtpd at company.com X-Spam-Processed: sm2.company.com, Tue, 12 Jan 2010 08:08:28 -0500 (not processed: message from trusted or authenticated source) X-MDRcpt-To: recipient@company.com X-MDRemoteIP: 17.1.6.6 X-Return-Path: sender@originating-server.org X-MDaemon-Deliver-To: recipient@company.com X-OriginalArrivalTime: 12 Jan 2010 13:09:20.0520 (UTC) FILETIME=[740B1880:01CA9388]

They are getting 5.2.1 bounce backs from a particular domain ONLY when the message originates from OWA or their iPhones(sent through Exchange profile). When the e-mail is sent from Outlook (or a 3rd party e-mail provider like GMail), the e-mail gets delivered fine..but OWA and the iPhones want to believe there is a problem.Headers below: (I changed names,usernames, and IP addresses to keep the message private, all other text is left as-is. This is just a wild guess (but an educated one from an earlier life working in the SMB space). The log mentions COMCAST and SBS.E-mail servers like Comcast and AOL have implemented a requirement for proper reverse lookups and PTRs for your domain before they will accept any incoming mail from your mail server.SBS users often start their life with a POP3 account and a .PST file. Then they are slowly moved to Exchange (with a POP3 Connector). Even with Exchange they might continue to send through their POP3 account and their ISP. This means they don't send through their Exchange profile. OWA and the iPhone with ActiveSync must use the Exchange profile. The ISP is accepted by COMCAST, the Exchange server not.If this theory is right, the Exchange server does not have any or a valid PTR record or uses a dynamic IP address with DynDNS or TZO. The solution should be to configure Exchange with a qualifying Smart Host.You can check the smart host here:Reverse DNS Lookup, Test reverse DNS (PTR) by IP address or hostnamehttp://www.myiptest.com/staticpages/index.php/Reverse-DNS-LookupMCTS: Messaging | MCSE: S+M | Small Business Specialist

Try the steps mentioned in here:http://www.it-eye.co.uk/faqs/readQuestion.php?qid=2