I'm currently trying to retrieve the RFT body of messages in Outlook
(from an app written in C#), and since that is, from what I gather, not
supported by the Outlook object model, I had to dig deeper into MAPI.
Now, I think I am on to something, but I am kind of stuck at one point:
It seems I can use the Function HrGetOneProp(...) to retrieve the value
of the PR_RTF_COMPRESSED property, which according to the documentation
is a pointer to an IStream object containing the compressed RTF. Now I
somehow need to pass this stream through the
WrapCompressedRTFStream(...) function to get a stream of UNcompressed
RTF, and according to what I found so far, I have to wrap the streams
into UCOMIStream, but I don't know how to create one of those from the
pointer I got from the call to HrGetOneProp.

Here's the relevant bit of my code:

  // Suppose we have a pointer to the IMAPIProp interface of the
  // MailItem object whose RTF body we want
  IntPtr pPropValue;
  HrGetOneProp(pIMAPIProp, PR_RTF_COMPRESSED, out pPropValue);
  PropValueStruct propValue = (PropValueStruct)Marshal.PtrToStructure(
     pPropValue, typeof(PropValueStruct));
  IntPtr pIStream = new IntPtr(propValue.value);
  UCOMIStream compressedStream = /* here, some magic happens */
  UCOMIStream uncompressedStream;
  WrapCompressedRTFStream(compressedStream, 0,
     out uncompressedStream);
  // Dump the contents of uncompressedStream somewhere usable,
  // and we're done.

The magic part in the middle eludes me. If anyone has any idea, I'd
love to hear it.