Exchange Server 2003 goes into Extended Support on 4/14/2009.
Details on our lifecycle policy for Exchange 2003 can be found at http://support.microsoft.com/lifecycle/?LN=en-us&p1=1773&x=11&y=9

Outlook 2003 goes into Extended Support on 4/14/2009.
http://support.microsoft.com/lifecycle/?p1=2520

We have seen a lot of applications that use Simple MAPI. Unlike Extended MAPI (or MAPI), it is supported in managed code as well.

Also, a lot developers have come across issues with Simple MAPI with Outlook 2007.
Starting with Outlook 2007, Simple MAPI is no longer supported. However, its still supported by Exchange 2003.
http://msdn.microsoft.com/en-us/library/cc815424.aspx

The article sheds light into how PST folder hierarchy is created.

Adding a PST to an existing profile doesn't create the all the Special Folders and looks as below:



We have the IPM Root, Common Views, Search Results, Deleted Items under the "Top of Personal Folders".
In short, the IPM subtree doesn't gets fully constructed which should include Outbox folder, Sent Items Folder and the Receive folder like the Inbox.

However, if the PST is set as the Default folder, we will see all the eight special folders that are part of IPM subtree are created and usually cannot be deleted in Outlook.

 

For those, who don't use Exchange Web Services API, but bank on its Requests and Responses.

An email message has a attachment table that contains the attachments, and these in turn contain the properties such as PR_ATTACH_SIZE, PR_ATTACH_DATA_BIN etc. This means that email message doesn't have any of the attachment properties on it.

The GetItem could be used to get the all the properties of an email message, the extended properties being got by PathToExtendedFieldType.

The GetAttachment doesn't get the PR_ATTACH_SIZE MAPI Property when being given the Attachment ID. The size could be found by using the Length property of the Content fetched in the byte array.

This is also validated with PathToExtendedFieldType, which when usen in GetAttachment request doesn't send back the PR_ATTACH_SIZE.

GetAttachmentType getAttachmentRequest = new GetAttachmentType();
getAttachmentRequest.AttachmentShape = new AttachmentResponseShapeType();
PathToExtendedFieldType pteftFlagStatus = new PathToExtendedFieldType();
pteftFlagStatus.PropertyTag = "0x0E20"; // Tag of PR_ATTACH_SIZE
pteftFlagStatus.PropertyType = MapiPropertyTypeType.Long;

REQUEST
<?xml version="1.0"?>
  <GetAttachmentType xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <AttachmentShape xmlns="http://schemas.microsoft.com/exchange/services/2006/messages">
      <AdditionalProperties xmlns="http://schemas.microsoft.com/exchange/services/2006/types">
        <ExtendedFieldURI PropertyTag="0x0E20" PropertyType="Long" />
      </AdditionalProperties>
    </AttachmentShape>
    <AttachmentIds xmlns="http://schemas.microsoft.com/exchange/services/2006/messages">
    <AttachmentId Id="AAAaAEFkbWluaXN0cmF0b3JAZGMxMjkw...</AttachmentIds>
</GetAttachmentType>

RESPONSE
<?xml version="1.0"?>
  <GetAttachmentResponseType xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <ResponseMessages xmlns="http://schemas.microsoft.com/exchange/services/2006/messages">
      <GetAttachmentResponseMessage ResponseClass="Success">
        <ResponseCode>NoError</ResponseCode>
          <Attachments>
           <FileAttachment xmlns="http://schemas.microsoft.com/exchange/services/2006/types">
             <AttachmentId Id="AAAaAEFkbWluaXN0cmF0b3JAZG...<Name>smime.p7m</Name>
                 <ContentType>multipart/signed</ContentType>
                   <Content>TUlNRS1WZXJza.....
                   </Content>
           </FileAttachment>
          </Attachments>
      </GetAttachmentResponseMessage>
    </ResponseMessages>
</GetAttachmentResponseType>

There we go. The response doesn't yield the Extended Field type property.
Hence, the theorem.

Futher to SGriffin's Weblog as below:
http://blogs.msdn.com/stephen_griffin/archive/2007/02/09/exchange-web-services-and-internet-message-headers.aspx

in order to access the body of an email message, the MAPI property PR_BODY_HTML (0x1013) could be used.
However, we need to remember the property is binary in nature and base64 encoded.
Here comes Convert.FromBase64String, System.Text.ASCIIEncoding to our rescue using which the ASCII of the body could be got, as below:
 
  byte [] bAscii = Convert.FromBase64String(it.ExtendedProperty[0].Item.ToString());
  System.Text.ASCIIEncoding enc = new System.Text.ASCIIEncoding();
  string str = enc.GetString(bAscii);

/* Source Code */
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Text;
using System.Net;
using System.IO;
using System.Xml.Serialization;
using WebServices1.localhost;

namespace WebServices1
{
  class Program
  {
    static void Main(string[] args)
    {
      ExchangeServiceBinding esb = new ExchangeServiceBinding();
      esb.Credentials = new NetworkCredential("username", "password", "domain");
      esb.Url = @http://localhost/EWS/Exchange.asmx;
      DistinguishedFolderIdType[] folderIDArray = new DistinguishedFolderIdType[1];
      folderIDArray[0] = new DistinguishedFolderIdType();
      folderIDArray[0].Id = DistinguishedFolderIdNameType.inbox;
      //set the props that we want to retrieve
      FolderResponseShapeType frst = new FolderResponseShapeType();
      frst.BaseShape = DefaultShapeNamesType.AllProperties;
      GetFolderType myfoldertype = new GetFolderType();
      myfoldertype.FolderIds = folderIDArray;
      myfoldertype.FolderShape = frst;
      Console.WriteLine("Getting inbox");
      GetFolderResponseType myFolder = esb.GetFolder(myfoldertype);
      FolderInfoResponseMessageType firmtInbox = (FolderInfoResponseMessageType)myFolder.ResponseMessages.Items[0];
      Console.WriteLine("got folder: {0}", firmtInbox.Folders[0].DisplayName);
      PathToUnindexedFieldType ptuftSubject = new PathToUnindexedFieldType();
      ptuftSubject.FieldURI = UnindexedFieldURIType.itemSubject;
      PathToExtendedFieldType pteftFlagStatus = new PathToExtendedFieldType();
      pteftFlagStatus.PropertyTag = "0x1013"; // PR_BODY_HTML
      pteftFlagStatus.PropertyType = MapiPropertyTypeType.Binary;
      FindItemType findItemRequest = new FindItemType();
      findItemRequest.Traversal = ItemQueryTraversalType.Shallow;
      findItemRequest.ItemShape = new ItemResponseShapeType();
      findItemRequest.ItemShape.BaseShape = DefaultShapeNamesType.AllProperties;
      findItemRequest.ItemShape.AdditionalProperties = new BasePathToElementType[2];
      findItemRequest.ItemShape.AdditionalProperties[0] = ptuftSubject;
      findItemRequest.ItemShape.AdditionalProperties[1] = pteftFlagStatus;
      findItemRequest.ParentFolderIds = new FolderIdType[] { firmtInbox.Folders[0].FolderId };
      FindItemResponseType firt = esb.FindItem(findItemRequest);
      foreach (FindItemResponseMessageType firmtMessage in firt.ResponseMessages.Items)
      {
        if (null != firmtMessage.RootFolder && firmtMessage.RootFolder.TotalItemsInView > 0)
        {
          foreach (ItemType it in ((ArrayOfRealItemsType)firmtMessage.RootFolder.Item).Items)
          {
            Console.WriteLine("got item subject: {0}", it.Subject);
            if (null != it.ExtendedProperty)
            {
              Console.WriteLine("Prop PR_BODY_HTML(Binary): {0}", it.ExtendedProperty[0].Item.ToString());
              byte [] bAscii = Convert.FromBase64String(it.ExtendedProperty[0].Item.ToString());
              Console.WriteLine();
              System.Text.ASCIIEncoding enc = new System.Text.ASCIIEncoding();
              string str = enc.GetString(bAscii);
              Console.WriteLine("Prop PR_BODY_HTML(ASCII): {0}", str);
            }
            else
            {
              Console.WriteLine("Prop PR_BODY_HTML: not found");
            }
          }
        }
      }
      Console.WriteLine("\nHit any key to continue");
      Console.ReadKey(true);
    }
  }
}

As mentioned in the http://support.microsoft.com/kb/266353, programmatically reading MAPI properties by using APIs such as Extended MAPI the PropertyAccessor object in the Microsoft Office Outlook 2007 object model is supported.
Here's how we do it in C++.

#pragma warning(disable:4146)

#import "C:\Windows\System32\stdole2.tlb" rename_namespace("Outlook")
#import "C:\Program Files\Common Files\Microsoft Shared\OFFICE12\mso.dll" rename_namespace("Outlook")
#import "C:\Program Files\Microsoft Office\OFFICE12\msoutl.olb" rename_namespace("Outlook")

#pragma warning(default:4146)

#include <stdio.h>
#include <tchar.h>

using namespace Outlook;

struct StartOle
{
 StartOle()
 {
  CoInitialize(NULL);
 }

 ~StartOle()
 {
  CoUninitialize();
 }
}_inst_StartOle;

void dump_com_error(_com_error &e)
{
    _tprintf(_T("Oops - hit an error!\n"));
    _tprintf(_T("\a\tCode = %08lx\n"), e.Error());
    _tprintf(_T("\a\tCode meaning = %s\n"), e.ErrorMessage());
    _bstr_t bstrSource(e.Source());
    _bstr_t bstrDescription(e.Description());
    _tprintf(_T("\a\tSource = %s\n"), (LPCTSTR) bstrSource);
    _tprintf(_T("\a\tDescription = %s\n"), (LPCTSTR) bstrDescription);
}

void main(int argc, char* argv[])
{
 try
 {
  _ApplicationPtr pApp("Outlook.Application");
  
  _NameSpacePtr pNameSpace;
  pNameSpace = pApp->GetNamespace(L"MAPI");

  MAPIFolderPtr pAppointmentMAPIFolder;
  
  pAppointmentMAPIFolder = pNameSpace->GetDefaultFolder(olFolderCalendar);

  _ItemsPtr pItems;
  _AppointmentItemPtr pAppointmentItem;

  pItems = pAppointmentMAPIFolder->GetItems();

  printf("No of items : %d\n", pItems->Count);

  pAppointmentItem = pItems->GetFirst();

  /* The following code uses GetPropertyAccessor: gets the user property WORKS */

  _PropertyAccessorPtr pPropAccPtr;
  pPropAccPtr = pAppointmentItem->GetPropertyAccessor();
  _variant_t var;
  var = pPropAccPtr->GetProperty(L"http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-c000-000000000046}/SomeID");

  /* The following code uses GetUserProperties: does not get the user property DOES NOT WORK */

  //UserPropertiesPtr pUP;
  //pUP = pAppointmentItem->GetUserProperties();
  //UserPropertyPtr uPP = pUP->Item(L"SomeID");
  //_variant_t var;
  //var = pPropAccPtr->GetProperty(L"http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-c000-000000000046}/SomeID");
  //var = uPP->GetValue();
  
 }
 catch(_com_error &e)
 {
  dump_com_error(e);
 }
}