diff --git a/mozilla/mail/app/profile/mailnews.js b/mozilla/mail/app/profile/mailnews.js
index 3beb28ab69e..78cca1678d6 100644
--- a/mozilla/mail/app/profile/mailnews.js
+++ b/mozilla/mail/app/profile/mailnews.js
@@ -499,3 +499,6 @@ pref("mail.purge.min_delay",480);
 // "mail.purge.timer_interval", fire the purge timer every 5 minutes, starting 5 minutes after we load accounts
 pref("mail.purge.timer_interval",5);
 pref("mailnews.view.last",0); // 0 == "all" view
+
+// require a password before showing imap or local headers in thread pane
+pref("mail.password_protect_local_cache", false);
diff --git a/mozilla/mail/base/content/commandglue.js b/mozilla/mail/base/content/commandglue.js
index 82eeb521c97..9ce604dda1e 100644
--- a/mozilla/mail/base/content/commandglue.js
+++ b/mozilla/mail/base/content/commandglue.js
@@ -210,7 +210,13 @@ function ChangeFolderByURI(uri, viewType, viewFlags, sortType, sortOrder)
   var showMessagesAfterLoading;
   try {
     var server = msgfolder.server;
-    if (server.redirectorType) {
+    if (gPrefs.getBoolPref("mail.password_protect_local_cache"))
+    {
+      showMessagesAfterLoading = !server.isAuthenticated;
+      // servers w/o passwords (like local mail) will always be non-authenticated.
+      // So we need to use the account manager for that case.
+    }
+    else if (server.redirectorType) {
       var prefString = server.type + "." + server.redirectorType + ".showMessagesAfterLoading";
       showMessagesAfterLoading = gPrefs.getBoolPref(prefString);
     }