this is actually a continuation from http://social.technet.microsoft.com/Forums/en-US/exchangesvrgeneral/thread/71ad755e-10c8-4586-9b17-6e020785c2c9 I have managed to enable pipeline tracing and captured the incoming mail and conpared to the received mail. This is the original.eml ========== X-CreatedBy: MessageSnapshot-Begin injected headers X-MessageSnapshot-UTC-Time: 2011-07-08T05:14:22.618Z X-MessageSnapshot-Protocol-Id: 08CE0ADDBDB6FC41;2011-07-08T05:14:22.602Z;1 X-MessageSnapshot-Source: Original X-Sender: sender@senderdomain.com X-Receiver: recipient@recipientdomain.com X-EndOfInjectedXHeaders: MessageSnapshot-End injected headers Received: from server1.recipientdomain.local (192.168.159.10) by server2.recipientdomain.local (192.168.159.68) with Microsoft SMTP Server id 7.8.9.0; Fri, 8 Jul 2011 13:14:22 +0800 Message-ID: <15650f3200000df3@recipientdomain.local> X-TM-IMSS-Message-ID: <15650f3200000df3@recipientdomain.local> Received: from svr1.senderdomain.com ([1.2.3.4]) by recipientdomain.local ([192.168.159.10]) with ESMTP (TREND IMSS SMTP Service 7.1) id 15650f3200000df3 ; Fri, 8 Jul 2011 13:15:03 +0800 Received: by svr1.senderdomain.com (Postfix, from userid 502) id 6AC5913881DF; Fri, 8 Jul 2011 13:15:02 +0800 (SGT) To: "'recipient name'" <recipient@recipientdomain.com> Subject: Re: [#1053292] Subject Header MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: base64 X-TM-AS-Product-Ver: IMSS-7.1.0.1394-6.8.0.1017-18246.004 X-TM-AS-Result: No--13.750-5.0-31-1 X-imss-scan-details: No--13.750-5.0-31-1 Content-Type: text/plain From: <sender@senderdomain.com> Return-Path: sender@senderdomain.com Date: Fri, 8 Jul 2011 13:14:22 +0800 X-MS-Exchange-Organization-OriginalArrivalTime: 08 Jul 2011 05:14:22.6338 (UTC) X-MS-Exchange-Forest-ArrivalHubServer: server2.recipientdomain.local X-MS-Exchange-Organization-OriginalClientIPAddress: 192.168.159.10 X-MS-Exchange-Organization-OriginalServerIPAddress: 192.168.159.68 X-MS-Exchange-Organization-AuthSource: server2.recipientdomain.local X-MS-Exchange-Organization-AuthAs: Anonymous X-MS-Exchange-Organization-MessageDirectionality: Incoming b3JpZ2luYWwgY29udGVudCBoYXMgYmVlbiByZW1vdmVkIGFuZCBpbnNlcnRlZCB3aXRoIHJhbmRvbSBzdHVmZg== ========== and this is the email received by the user ========== Received: from server1.recipientdomain.local (192.168.159.10) by server2.recipientdomain.local (192.168.150.68) with Microsoft SMTP Server id 7.8.9.0; Fri, 8 Jul 2011 13:14:22 +0800 Received: from svr1.senderdomain.com ([1.2.3.4]) by recipientdomain.local ([192.168.150.10]) with ESMTP (TREND IMSS SMTP Service 7.1) id 15650f3200000df3 ; Fri, 8 Jul 2011 13:15:03 +0800 Received: by svr1.senderdomain.com (Postfix, from userid 502) id 6AC5913881DF; Fri, 8 Jul 2011 13:15:02 +0800 (SGT) From: "sender@senderdomain.com" <sender@senderdomain.com> To: recipient name <recipient@recipientdomain.com> Subject: Re: [#1053292] Subject Header Thread-Topic: [#1053292] Subject Header Thread-Index: AQHMPS3lgzbj0eGK6karAQxIJNlMzg== Date: Fri, 8 Jul 2011 05:14:22 +0000 Message-ID: <15650f3200000df3@recipientdomain.local> Content-Language: en-SG X-MS-Has-Attach: X-MS-Exchange-Organization-SCL: 0 X-MS-TNEF-Correlator: x-tm-as-result: No--28.649600-8.000000-31 x-tm-as-product-ver: SMEX-10.0.0.4211-6.800.1017-18246.003 x-tm-as-user-blocked-sender: No x-tm-as-user-approved-sender: No x-imss-scan-details: No--13.750-5.0-31-1 x-tm-imss-message-id: <15650f3200000df3@recipientdomain.local> Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 b3JpZ2luYWwgY29udGVudCBoYXMgYmVlbiByZW1vdmVkIGFuZCBpbnNlcnRlZCB3aXRoIHJhbmRvbSBzdHVmZg== ========== It is noted that the Content-Transfer-Encoding had been changed from Base64 to quoted-printable but the content was not decoded and encoded to quoted-printable. The following is also observed Issue only occurs to Ex 2010 mailbox but not Ex 2003 mailbox Issue only occurs when receiving from sender@senderdomain.com but not other senders from senderdomain.com I am running out of idea and appreciate if someone can provide furthur troubleshooting steps. Thanks!