android know when mail was sent and do action after sending

Question

Im sending an email from my android app

                  Intent email = new Intent(Intent.ACTION_SEND);
                  email.putExtra(Intent.EXTRA_EMAIL, new String[]{ to});
                                  email.putExtra(Intent.EXTRA_SUBJECT, subject);
                  email.putExtra(Intent.EXTRA_TEXT, message);

                  //attachment
                  Uri uri = Uri.fromFile(new File(Environment.getExternalStorageDirectory(), "generato.pdf"));
                  email.putExtra(Intent.EXTRA_STREAM, uri);

                  //need this to prompts email client only
                  email.setType("message/rfc822");

                  startActivity(Intent.createChooser(email, "Choose an Email client :"));

How can I know when the "composer" window has been dismissed after sending mail so I can start another action?

Thanks!