Previous checking for Bug 343059 was a patch by Serge Gautherie <gautheri@noos.fr>

mailnews/base/resources/content/phishingDetector.js

@@ -114,7 +114,7 @@ function isPhishingURL(aLinkNode, aSilentMode, aHref)
   {
     unobscuredHostName.value = hrefURL.host;
 
-    if (hostNameIsIPAddress(hrefURL.host, unobscuredHostName))
+    if (hostNameIsIPAddress(hrefURL.host, unobscuredHostName) && !isLocalIPAddress(unobscuredHostName))
       phishingType = kPhishingWithIPAddress;
     else if (misMatchedHostWithLinkText(aLinkNode, hrefURL, linkTextURL))
       phishingType = kPhishingWithMismatchedHosts;
@@ -243,3 +243,14 @@ function confirmSuspiciousURL(aPhishingType, aSuspiciousHostName)
   var buttons = nsIPS.STD_YES_NO_BUTTONS + nsIPS.BUTTON_POS_1_DEFAULT;
   return promptService.confirmEx(window, titleMsg, dialogMsg, buttons, "", "", "", "", {}); /* the yes button is in position 0 */
 }
+
+// returns true if the IP address is a local address.
+function isLocalIPAddress(unobscuredHostName)
+{
+  var ipComponents = unobscuredHostName.value.split(".");
+
+  return ipComponents[0] == 10 ||
+         (ipComponents[0] == 192 && ipComponents[1] == 168) ||
+         (ipComponents[0] == 169 && ipComponents[1] == 254) ||
+         (ipComponents[0] == 172 && ipComponents[1] >= 16 && ipComponents[1] < 32);
+}