Answer by Ryan Heitner for Sending Email in Android using JavaMail API without using the default/built-in app

In order to help those getting a Network On Main Thread Exception with an SDK Target >9. This is using droopie's code above but will work similarly for any.

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();StrictMode.setThreadPolicy(policy); android.os.NetworkOnMainThreadException

You can use AsyncTask as below

public void onClickMail(View view) {    new SendEmailAsyncTask().execute();}class SendEmailAsyncTask extends AsyncTask <Void, Void, Boolean> {    Mail m = new Mail("from@gmail.com", "my password");    public SendEmailAsyncTask() {        if (BuildConfig.DEBUG) Log.v(SendEmailAsyncTask.class.getName(), "SendEmailAsyncTask()");        String[] toArr = { "to mail@gmail.com"};        m.setTo(toArr);        m.setFrom("from mail@gmail.com");        m.setSubject("Email from Android");        m.setBody("body.");    }    @Override    protected Boolean doInBackground(Void... params) {        if (BuildConfig.DEBUG) Log.v(SendEmailAsyncTask.class.getName(), "doInBackground()");        try {            m.send();            return true;        } catch (AuthenticationFailedException e) {            Log.e(SendEmailAsyncTask.class.getName(), "Bad account details");            e.printStackTrace();            return false;        } catch (MessagingException e) {            Log.e(SendEmailAsyncTask.class.getName(), m.getTo(null) +"failed");            e.printStackTrace();            return false;        } catch (Exception e) {            e.printStackTrace();            return false;        }    }