--- a/calendar/base/modules/calAuthUtils.jsm
+++ b/calendar/base/modules/calAuthUtils.jsm
@@ -299,13 +299,16 @@ cal.auth.Prompt.prototype = {
                 aCallback.onAuthAvailable(aContext, aAuthInfo);
             },
 
             onPromptCanceled : function() {
                 aCallback.onAuthCancelled(aContext, true);
             }
         };
 
+
+        let hostKey = (aChannel.URI.host + ":" + aChannel.URI.port + " (" + aAuthInfo.realm + ")");
+
         var asyncprompter = Components.classes["@mozilla.org/messenger/msgAsyncPrompter;1"]
                                       .getService(Components.interfaces.nsIMsgAsyncPrompter);
-        asyncprompter.queueAsyncAuthPrompt(aChannel.URI.spec, false, promptlistener);
+        asyncprompter.queueAsyncAuthPrompt(hostKey, false, promptlistener);
     }
 };