uses
shellapi;
procedure TForm1.Button1Click(Sender: TObject);
var
em_subject, em_body, em_mail : string;
begin
em_subject := 'Test Message';
em_body := 'Hello this is a test Message from Shell Execute Command to Open the Default Mail Wndow';
em_mail := 'mailto:jdhiraj@rediffmail.com?subject=' +
em_subject + '&body=' + em_body ;
ShellExecute(Handle,'open',
PChar(em_mail), nil, nil, SW_SHOWNORMAL);
end;