server/apps/spring-app/src/main/resources/dnsservice.xml

<?xml version="1.0"?>
<!--
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  regarding copyright ownership.  The ASF licenses this file   
  to you under the Apache License, Version 2.0 (the            
  "License"); you may not use this file except in compliance   
  with the License.  You may obtain a copy of the License at   
                                                               
    http://www.apache.org/licenses/LICENSE-2.0                 
                                                               
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  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       
  KIND, either express or implied.  See the License for the    
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  under the License.                                           
 -->
 
<!--
   This template file can be used as example for James Server configuration
   DO NOT USE IT AS SUCH AND ADAPT IT TO YOUR NEEDS
-->
 
<!-- See http://james.apache.org/server/3/config.html for usage -->

<!-- DNS Service Block -->
<!-- -->
<!-- Specifies DNS Server information for use by various components inside -->
<!-- James. -->
<!-- -->
<!-- If autodiscover is true, James will attempt to autodiscover the DNS servers configured on your underlying system.-->
<!-- Currently, this works if the OS has a unix-like /etc/resolv.conf,-->
<!-- or the system is Windows based with ipconfig or winipcfg.-->
<!-- -->
<!-- If no DNS servers are found and you have not specified any below, 127.0.0.1 will be used-->
<!-- If you use autodiscover and add DNS servers manually a combination of all the dns servers will be used  -->
<!--  -->
<!-- Information includes a list of DNS Servers to be used by James.  These are -->
<!-- specified by the server elements, each of which is a child element of the -->
<!-- servers element.  Each server element is the IP address of a single DNS server. -->
<!-- The servers element can have multiple server children. -->
<dnsservice>
   <servers>
       <!--Enter ip address of your DNS server, one IP address per server -->
       <!-- element. -->
       <!--
       <server>127.0.0.1</server>
        -->
   </servers>
   <!-- Change autodiscover to false if you would like to turn off autodiscovery -->
   <!-- and set the DNS servers manually in the<servers>section -->
   <autodiscover>true</autodiscover>
   <authoritative>false</authoritative>

   <!-- Maximum number of entries to maintain in the DNS cache -->
   <maxcachesize>50000</maxcachesize>
      
   <!-- Uncomment this if you want James to try a single server for each -->
   <!-- multihomed mx host. -->
   <!--
   <singleIPperMX>true</singleIPperMX>
    -->
</dnsservice>