Intent emailIntent = new Intent(Intent.ACTION_SENDTO, Uri.fromParts("mailto","correo@gmail.com", null));
                emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Android APP - ");
                startActivity(Intent.createChooser(emailIntent,  getActivity().getString(R.string.enviar_mail)));

String[] TO = {""}; //Direcciones email  a enviar.
  String[] CC = {""}; //Direcciones email con copia.

  Intent emailIntent = new Intent(Intent.ACTION_SEND);

  emailIntent.setData(Uri.parse("mailto:"));
  emailIntent.setType("text/plain");
  emailIntent.putExtra(Intent.EXTRA_EMAIL, TO);
  emailIntent.putExtra(Intent.EXTRA_CC, CC);
  emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Tu Asunto...");
  emailIntent.putExtra(Intent.EXTRA_TEXT, "tuemail@email.com"); // * configurar email aquí!

  try {
     startActivity(Intent.createChooser(emailIntent, "Enviar email."));
     Log.i("EMAIL", "Enviando email...");
  }
  catch (android.content.ActivityNotFoundException e) {
     Toast.makeText(this, "NO existe ningún cliente de email instalado!.", Toast.LENGTH_SHORT).show();
  }

repositories {
     jcenter()
     maven {
         url "https://maven.java.net/content/groups/public/"
     }
 }

dependencies {
     compile 'com.sun.mail:android-mail:1.5.5'
     compile 'com.sun.mail:android-activation:1.5.5'
 }

/**
 * Created by snolde on 06-04-2017.
 */

public class MailJob extends AsyncTask<MailJob.Mail,Void,Void>{
    private final String user;
    private final String pass;

    public MailJob(String user, String pass) {
        super();
        this.user=user;
        this.pass=pass;
    }

    @Override
    protected Void doInBackground(Mail... mails) {
        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props,
                new javax.mail.Authenticator() {
                    protected PasswordAuthentication getPasswordAuthentication() {
                        return new PasswordAuthentication(user, pass);
                    }
                });
        for (Mail mail:mails) {

            try {

                Message message = new MimeMessage(session);
                message.setFrom(new InternetAddress(mail.from));
                message.setRecipients(Message.RecipientType.TO,
                        InternetAddress.parse(mail.to));
                message.setSubject(mail.subject);
                message.setText(mail.content);

                Transport.send(message);

            } catch (MessagingException e) {
                Log.d("MailJob", e.getMessage());
            }
        }
        return null;
    }

    public static class Mail{
        private final String subject;
        private final String content;
        private final String from;
        private final String to;

        public Mail(String from, String to, String subject, String content){
            this.subject=subject;
            this.content=content;
            this.from=from;
            this.to=to;
        }
    }
}

new MailJob(user, passwd).execute(
              new MailJob.Mail("from@gmail.com", "to@otromail.com", "subjeto", "contenido")
            );