Hi All,
I have created a plug-in for outlook. Plug-in has only below code.
    private void OnNewOutlookInspector(Outlook.Inspector OutlookInsptr)
        {          
            Outlook.MailItem MlItem = (Outlook.MailItem)OutlookInsptr.CurrentItem;
            //if I remove below line. Everything is working fine.
            MlItem.UserProperties.Add("INSPINIT", Outlook.OlUserPropertyType.olText   , true , true ).Value = "1";            
        }
  public void OnConnection(object application, Extensibility.ext_ConnectMode connectMode, object addInInst, ref System.Array custom)
  {
   applicationObject = application;
   addInInstance = addInInst;
            MessageBox.Show("in connection new 2");
            OutlkApp = (Outlook.Application)application;
            OutlkInsptrs = OutlkApp.Inspectors;
            OutlkInsptrs.NewInspector += new Outlook.InspectorsEvents_NewInspectorEventHandler(OnNewOutlookInspector);
  }
Problem I am facing is, When I send HTML mail while plug-in is enabled, receiving end it is being received as a plain text. Below is the mail content along with the header and body at recieving end.
    x-sender: 
[email protected]
x-receiver: 
[email protected]
Received: from blr-s-07.pointcrossblr.com ([192.168.1.107]) by blr-ws-134.pointcrossblr.com with Microsoft 
SMTPSVC(6.0.2600.5949);
  Wed, 22 Dec 2010 17:11:02 +0530
Received: from blrws134 ([192.168.1.175]) by blr-s-07.pointcrossblr.com with Microsoft SMTPSVC(6.0.3790.4675);
  Wed, 22 Dec 2010 17:11:02 +0530
From: "Ashif Nataliya" <
[email protected]>
To: <
[email protected]>
Cc: <
[email protected]>
Subject: RTF FRM blr to pc.com cc blr-ws-134
Date: Wed, 22 Dec 2010 17:11:02 +0530
Message-ID: <
[email protected]>
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="----=_NextPart_000_00F7_01CBA1FB.36115580"
X-Mailer: Microsoft Outlook 14.0
Content-Language: en-us
X-MS-TNEF-Correlator: 00000000DCB2344DE8F50F4FBC91085BB5C06D55A4172000
thread-index: AcuhzRuTOBkvHPUnS1aLi9+cHNAWhA==
Return-Path: 
[email protected]
X-OriginalArrivalTime: 22 Dec 2010 11:41:02.0822 (UTC) FILETIME=[1C788860:01CBA1CD]
This is a multipart 
message in MIME format.
------=_NextPart_000_00F7_01CBA1FB.36115580
Content-Type: text/plain;
 charset="us-ascii"
Content-Transfer-Encoding: 7bit
HTML Test
Test Mail
------=_NextPart_000_00F7_01CBA1FB.36115580
Content-Type: application/ms-tnef;
 name="winmail.dat"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="winmail.dat" 
   // and some other code.....
Any help is appreciated. Thanks.