procedure TForm1.LoadAttToStream( att: IAttachment );
var
  i: integer;
  lbound: integer;
  ubound: Integer;
  len: integer;
  buffer: array of byte;
  myarray: OleVariant;
  stream: TMemoryStream;
begin

  myarray := att.Content;
  lbound := VarArrayLowBound(myarray, 1 );
  ubound := VarArrayHighBound(myarray, 1 );
  len := ubound - lbound + 1;
  if len = 0 then
    exit;

  SetLength( buffer, len );
  for i := VarArrayLowBound(myarray, 1 ) to ubound do
  begin
     buffer[i] := VarArrayGet( myarray, i );
  end;

  stream := TMemoryStream.Create();

  stream.WriteBuffer( buffer[0], len );
  stream.SaveToFile( 'c:\my folder\' + att.Name ); //save stream to file.
  stream.Free();
end;