HttpWebResponse res = …;
MemoryStream httpStream = …;
MemoryStream mimeStream = …;
Encoding utf8 = Encoding.UTF8;
TextReader readerReq = new StreamReader(httpStream, utf8);
TextWriter writer = new StreamWriter(mimeStream, utf8);

// create a correct mime stream form the HttpResponseStream
// add http headers which were required for a correct mime
// format
writer.WriteLine("Date: " + res.GetResponseHeader("Date"));
writer.WriteLine("Content-Type: " + res.ContentType);
writer.WriteLine("Content-Length: " + res.ContentLength);
writer.WriteLine(Environment.NewLine);

// copy rest of the stream
while (true)
{
      string line = readerReq.ReadLine();
      if (line == null)
      {
                break;
      }
      writer.WriteLine(line);
}
writer.Flush();
mimeStream.Position =  0 ;

// parse  the stream for mime attachments
SharpMessage message = new SharpMessage(mimeStream,
   SharpDecodeOptions.Default | SharpDecodeOptions.DecodeTnef |
   SharpDecodeOptions.UuDecode);

MemoryStream httpStream = …;
MemoryStream mimeStream = …;