public class SendMail extends AsyncTask<Void, Void, Void> {

//Declaring Variables
private Context context;
private Session session;

//Information to send email
private String email;
private String subject;
private String message;

//Progressdialog to show while sending email
private ProgressDialog progressDialog;

//Class Constructor
public SendMail(Context context, String email, String subject, String message) {
    //Initializing variables
    this.context = context;
    this.email = email;
    this.subject = subject;
    this.message = message;
}

@Override
protected void onPreExecute() {
    super.onPreExecute();
    //Showing progress dialog while sending email
    progressDialog = ProgressDialog.show(context, "Sending message", "Please wait...", false, false);
}

@Override
protected void onPostExecute(Void aVoid) {
    super.onPostExecute(aVoid);
    //Dismissing the progress dialog
    progressDialog.dismiss();
    //Showing a success message
    Toast.makeText(context, "Message Sent", Toast.LENGTH_LONG).show();
}

@Override
protected Void doInBackground(Void... params) {

    String prot = "smtp";
    final String user = Config.EMAIL;
    String to = Config.EMAIL;
    final String pass = Config.PASSWORD;
    String mailhost = "smtp-mail.outlook.com";

    Properties props = System.getProperties();
    props.put("mail." + prot + ".host", mailhost);
    props.put("mail." + prot + ".auth", "true");
    props.put("mail." + prot + ".starttls.enable", "true");
    props.put("mail." + prot + ".port", "587");
    props.put("mail." + prot + ".ssl.enable", "false");

    Session session = Session.getDefaultInstance(props,
            new javax.mail.Authenticator() {
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(user, pass);
                }
            });
    session.setDebug(true);

    try {
        Message msg = new MimeMessage(session);
        msg.setFrom(new InternetAddress(user));
        msg.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse(to, false));

        msg.setSubject("TESTE ENVIO EMAIL");

        msg.setText("Teste de envio de email conteudo");

        msg.setHeader("X-Mailer", user);
        msg.setSentDate(new Date());

        SMTPTransport t = (SMTPTransport) session.getTransport(prot);

        t.connect(mailhost, user, pass);

        t.sendMessage(msg, msg.getAllRecipients());
        t.close();

        Log.d("------------", "done");
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}