use net/dns2 for mx lookups

zimbraEmail_mx.php

@@ -1,6 +1,6 @@
 <?php
 use WHMCS\Database\Capsule;
-require "Net/DNS2.php";
+require "/usr/share/pear/Net/DNS2.php";
 // opcache_reset();
 
 function ZimbraEmail_ClientAreaCustomButtonArray ($params)