@Override
  public String toString() {
    StringBuilder buffer = new StringBuilder(200);
    buffer.append("[Mail Host: ");
    buffer.append(getMailHost());
    buffer.append("]");
    buffer.append(" [Mail From: ");
    buffer.append(getMailFromAddress());
    buffer.append("]");
    buffer.append(" [Mail To: ");
    if (mailToAddresses.length > 0) {

      for (final String mailToAddress : mailToAddresses) {
        buffer.append(mailToAddress);
        buffer.append(", ");
      }
      buffer.replace(buffer.length() - 2, buffer.length(), "");
    } else {
      buffer.append(" Undefined");
    }
    buffer.append("]");
    return buffer.toString();
  }
Set the mail properties, e.g mail host, mailFrom, MailTo etc
geode-core/src/main/java/org/apache/geode/admin/jmx/internal/MailManager.java