mailinabox/conf/mozilla-autoconfig.xml

<?xml version="1.0"?>
<clientConfig version="1.1">
    <emailProvider id="PRIMARY_HOSTNAME">
      <domain>PRIMARY_HOSTNAME</domain>

      <displayName>PRIMARY_HOSTNAME (Mail-in-a-Box)</displayName>
      <displayShortName>PRIMARY_HOSTNAME</displayShortName>

      <incomingServer type="imap">
         <hostname>PRIMARY_HOSTNAME</hostname>
         <port>993</port>
         <socketType>SSL</socketType>
         <username>%EMAILADDRESS%</username>
         <authentication>password-cleartext</authentication>
      </incomingServer>

      <outgoingServer type="smtp">
         <hostname>PRIMARY_HOSTNAME</hostname>
         <port>465</port>
         <socketType>SSL</socketType>
         <username>%EMAILADDRESS%</username>
         <authentication>password-cleartext</authentication>
         <addThisServer>true</addThisServer>
         <useGlobalPreferredServer>false</useGlobalPreferredServer>
      </outgoingServer>

      <documentation url="https://PRIMARY_HOSTNAME/">
         <descr lang="en">PRIMARY_HOSTNAME website.</descr>
      </documentation>
    </emailProvider>

    <webMail>
      <loginPage url="https://PRIMARY_HOSTNAME/mail/" />
      <loginPageInfo url="https://PRIMARY_HOSTNAME/mail/" >
        <username>%EMAILADDRESS%</username>
        <usernameField id="rcmloginuser" name="_user" />
        <passwordField id="rcmloginpwd" name="_pass" />
        <loginButton id="rcmloginsubmit" />
      </loginPageInfo>
    </webMail>

    <clientConfigUpdate url="https://PRIMARY_HOSTNAME/.well-known/autoconfig/mail/config-v1.1.xml" />

</clientConfig>