diff --git a/extensions/help/resources/locale/en-US/mail_help.xhtml b/extensions/help/resources/locale/en-US/mail_help.xhtml
index bc0a17012441..6b893cb89d4f 100644
--- a/extensions/help/resources/locale/en-US/mail_help.xhtml
+++ b/extensions/help/resources/locale/en-US/mail_help.xhtml
@@ -2556,6 +2556,12 @@
     folder through which you want to search.</li>
   <li>Select <q>Search subfolders</q> to include all subfolders in the
     search.</li>
+  <li>Select <q>Search local system</q> to search only messages from newsgroups
+    or IMAP accounts that have been saved locally.
+
+    <p><strong>Note</strong>: The checkbox will be disabled if it&apos;s not
+      possible to search remotely stored messages.</p>
+  </li>
   <li>Select which matching option Mail &amp; Newsgroups will use to search for
     messages that match all or at least one of the conditions (criteria) that
     you choose.</li>