gecko-dev/mailnews/base/prefs/resources/content/mailPrefsOverlay.xul

<?xml version="1.0"?>

<!DOCTYPE overlay [
<!ENTITY % mailPrefsOverlayDTD SYSTEM "chrome://messenger/locale/mailPrefsOverlay.dtd" >
%mailPrefsOverlayDTD;
]>

<overlay id="mailPrefsOverlay"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

  <script type="application/x-javascript">
  <![CDATA[
    var panel;
    if (panel != undefined) {
      switch(panel) 
      {
      case "chrome://communicator/content/pref/pref-scripts.xul":
        _elementIDs.push("javascriptAllowMailNews");
        _elementIDs.push("pluginAllowMailNews");
        break;
      case "chrome://communicator/content/pref/pref-appearance.xul":
        _elementIDs.push("generalStartupMail");
        break;
      case "chrome://cookie/content/pref-cookies.xul":
        _elementIDs.push("networkDisableCookieForMailNews");
        break;
      case "chrome://cookie/content/pref-images.xul":
        _elementIDs.push("networkImageDisableImagesInMailNews");
        break;
      }
    }
  ]]>
  </script>         

  <!-- javascript toggle for mail/news -->
  <groupbox id="javascriptPreferences">
    <checkbox id="javascriptAllowMailNews"
              label="&enbJsCheckMailNews.label;" accesskey="&enbJsCheckMailNews.accesskey;"
              pref="true" preftype="bool" prefstring="javascript.allow.mailnews"
              prefattribute="checked" oncommand="javascriptEnabledChange();" insertafter="javascriptAllowNavigator"/>
  </groupbox>
  <!-- plugin toggle for mail/news -->
  <groupbox id="pluginPreferences">
    <checkbox id="pluginAllowMailNews"
              label="&enbPluginCheckMailNews.label;" accesskey="&enbPluginCheckMailNews.accesskey;"
              pref="true" preftype="bool" prefstring="mailnews.message_display.allow.plugins"
              prefattribute="checked"/>
  </groupbox>

  <!-- mail startup toggle -->
  <groupbox id="generalStartupPreferences">           
    <checkbox id="generalStartupMail" wsm_persist="true" position="3"
              label="&mail.label;" accesskey="&mail.accesskey;"
              pref="true" preftype="bool" prefstring="general.startup.mail"
              prefattribute="checked"/>         
  </groupbox>
  <!--- cookie toggle for mail/news -->
  <page id="cookiesPanel">
    <checkbox id="networkDisableCookieForMailNews"
              label="&disableCookieForMailNews.label;" accesskey="&disableCookieForMailNews.accesskey;"
              preftype="bool" prefstring="network.cookie.disableCookieForMailNews"
              insertafter="networkCookieBehaviorSeparator"/>
  </page>
  <!--- image toggle for mail/news -->
  <groupbox id="imagesArea">
    <checkbox id="networkImageDisableImagesInMailNews"
              label="&disableImageInMailNews.label;" accesskey="&disableImageInMailNews.accesskey;"
              pref="true" preftype="bool" prefstring="mailnews.message_display.disable_remote_image"
              prefattribute="checked" insertafter="networkImagesBehaviorSeparator"/>
  </groupbox>



  <!-- category tree entries for mail/news -->
  <treechildren id="panelChildren">
    <treeitem container="true" id="mailnews" position="3">
      <treerow>       
        <treecell url="chrome://messenger/content/pref-mailnews.xul" label="&mail.label;"/> 
      </treerow>
      <treechildren id="messengerChildren">
        <treeitem>
          <treerow>
            <treecell url="chrome://messenger/content/pref-windows.xul" label="&windows.label;"/> 
          </treerow>
        </treeitem>
        <treeitem>
          <treerow>
            <treecell url="chrome://messenger/content/pref-viewing_messages.xul" label="&viewingMessages.label;"/> 
          </treerow>
        </treeitem>
        <treeitem>
          <treerow>
            <treecell url="chrome://messenger/content/pref-notifications.xul" label="&notifications.label;"/> 
          </treerow>
        </treeitem>
        <treeitem id="mailcomposepref">
          <treerow>
            <treecell url="chrome://messenger/content/messengercompose/pref-composing_messages.xul" label="&composingMessages.label;"/> 
          </treerow>
        </treeitem>
        <treeitem>
          <treerow>
            <treecell url="chrome://messenger/content/messengercompose/pref-formatting.xul" label="&format.label;"/> 
          </treerow>
        </treeitem>
        <treeitem id="mailaddressbookpref">
          <treerow>
            <treecell url="chrome://messenger/content/addressbook/pref-addressing.xul" label="&address.label;"/> 
          </treerow>
        </treeitem>
        <treeitem>
          <treerow>
            <treecell url="chrome://messenger/content/pref-labels.xul" label="&labels.label;"/>
          </treerow>
        </treeitem>
        <treeitem>
          <treerow>
            <treecell url="chrome://messenger/content/pref-receipts.xul" label="&return.label;"/>
          </treerow>
        </treeitem>
      </treechildren>
    </treeitem>
  </treechildren>
           
</overlay>