private boolean isValidMail(String email) {

    String EMAIL_STRING = "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@"
            + "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

    return Pattern.compile(EMAIL_STRING).matcher(email).matches();

}