Thanks for the Information.

Another question related to this is how do I return a Byte array in C++
as an output? In C# I can do this

Calling application (C#)
{
   byte[] attByteArray=null;
   test.GetAttachmentBinary(attachment, ref attByteArray);
}

C# Method that would return my Byte Array information.
public void GetAttachmentBinary(MAPICDO::Attachment pAttachment, ref
byte[] AttachmentData)
{
   ...
}

How do I do the same in C++? I want to have my calling Application be
the same C# application. But I want my GetAttachmentBinary method to be
in C++ .NET. How Would I define my C++ method so that it would return
the byte[]?

Obviously this won't work but it is what I want to do.
public void GetAttachmentBinary(MAPICDO::Attachment* pAttachment, out
byte[] AttachmentData)
{
   ...
   Byte attachmentArray[] = new Byte[attSize];

   Byte __pin* p = &attachmentArray[0];
   hr = streamUnk->Read(p, attSize, (ULONG*)&attSize);

   AttachmentData = attachmentArray;
}

Once again your help is greatly appreciated on this.

Thanks
Chris