用MapiSendMail是否可以发送html邮件，如何处理？

Question

Delphi 6 中我使用
//=================================
procedure SendMailWithAttachments(Recipients : String;Subject:String; NoteText:TStrings; Attachments : TStrings);
type
  TSZBuf = array[0..255] of char;
var
  RC : ULONG;
  Recip : TMapiRecipDesc;
  Mail : TMapiMessage;
  pAttachments : array of TMapiFileDesc;
  i, AttachmentCount : Integer;
begin
  with Recip do
  begin
    ulReserved := 0;
    ulRecipClass := MAPI_TO;
    lpszName := nil;
    lpszAddress := pchar(Recipients);
    ulEIDSize := 0;
    lpEntryID := nil;
  end;  if (Attachments = nil) or (Attachments.Count = 0) then
  begin
    AttachmentCount := 0;
    pAttachments := nil;
  end
  else
  begin
    AttachmentCount := Attachments.Count;
    SetLength(pAttachments, AttachmentCount);
    for i := 0 to AttachmentCount - 1 do
      with pAttachments[i] do
      begin
        ulReserved := 0;
        flFlags := 0;
        nPosition := Cardinal(-1);
        lpszPathName := AllocMem(sizeof(TSZBuf));
          StrPcopy(lpszPathName, Attachments[i]);
        lpszFileName := AllocMem(sizeof(TSZBuf));
          StrPcopy(lpszFileName, ExtractFileName(Attachments[i]));
        lpFileType := nil;
      end;
  end;  with Mail do
  begin
    ulReserved := 0;
    lpszSubject := Pchar(Subject);
    if NoteText <> nil then
      lpszNoteText := Pchar(NoteText.Text)
    else
      lpszNoteText := nil;    lpszMessageType := nil;
//    lpszMessageType := 'Text/HTML';
    lpszDateReceived := nil;
    lpszConversationID := nil;
    flFlags := 0;
    lpOriginator := nil;
    if Recipients = '' then nRecipCount := 0
    else nRecipCount := 1;
    lpRecips := @Recip;
    nFileCount := AttachmentCount;
    lpFiles := Pointer(pAttachments);
  end;  try
    RC := MapiSendMail(0, Application.Handle, Mail, MAPI_DIALOG +MAPI_LOGON_UI, 0);
    if RC <> SUCCESS_SUCCESS then
      ShowSendMailErr(RC);
  finally
    if AttachmentCount > 0 then
      for i := 0 to AttachmentCount - 1 do
      begin
        FreeMem(pAttachments[i].lpszPathName);
        FreeMem(pAttachments[i].lpszFileName);
      end;
    SetLength(pAttachments, 0);
  end;
end;
//=================================
我这样调用上边的过程
.....
IdMessage.Body.LoadFromFile('E:\zt.htm');
IdMessage.Encoding:=meMIME;
IdMessage.ContentType:='Text/HTML';// //multipart/mixed
IdMessage.ContentTransferEncoding:='Base64';
IdMessage.SaveToFile('d:\ddd.eml',false);
IdMessage.Body.LoadFromFile('d:\ddd.eml');
.....
SendMailWithAttachments(EMailAddress,Subject,IdMessage.Body,AttachmentFiles);
结果调出outlook express看到的邮件的内容是编好码的邮件内容,如下：Content-Type: Text/HTML
MIME-Version: 1.0
Content-Transfer-Encoding: Base64
Date: Wed, 3 Aug 2005 13:31:15 +0800PGh0bWw+DQoNCjxoZWFkPg0KPG1ldGEgaHR0cC1lcXVpdj0iQ29udGVudC1MYW5ndWFnZSIgY29u
dGVudD0iemgtY24iPg0KPG1ldGEgaHR0cC1lcXVpdj0iQ29udGVudC1UeXBlIiBjb250ZW50PSJ0
ZXh0L2h0bWw7IGNoYXJzZXQ9Z2IyMzEyIj4NCjxtZXRhIG5hbWU9IkdFTkVSQVRPUiIgY29udGVu
dD0iTWljcm9zb2Z0IEZyb250UGFnZSA0LjAiPg0KPG1ldGEgbmFtZT0iUHJvZ0lkIiBjb250ZW50
PSJGcm9udFBhZ2UuRWRpdG9yLkRvY3VtZW50Ij4NCjx0aXRsZT5NYWd0ZWNossmx4M+1zbPNvLHq
.....
.....
L3RyPg0KICA8dHI+DQogICAgPHRkIHdpZHRoPSIxMDAlIiBhbGlnbj0icmlnaHQiIGNvbHNwYW49
IjIiIGhlaWdodD0iMjciPjxmb250IHNpemU9IjIiPjxhIGhyZWY9Imh0dHA6Ly93d3cubWFndGVj
aC5jb20uY24iPr60x+u52NeisbG+qcLquPHMqb/Lv8a8vLei1bnT0M/euavLvtfu0MKy+sa3us28
vMr1PC9hPjwvZm9udD48L3RkPg0KICA8L3RyPg0KPC90YWJsZT4NCg0KPC9ib2R5Pg0KDQo8L2h0
bWw+DQo=
.
但是把上边的内容保存为一个邮件比如aaa.eml用outlook express打开是正常的html格式的邮件
请问怎样才能使调出的outlook express生成的邮件能正常地显示为html邮件？