Not part of the build yet!! I converted nsIMsgMailNewsUrl.h into an idl file.

mailnews/base/public/nsIMsgMailNewsUrl.idl

@@ -0,0 +1,62 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "NPL"); you may not use this file except in
+ * compliance with the NPL.  You may obtain a copy of the NPL at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the NPL is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
+ * for the specific language governing rights and limitations under the
+ * NPL.
+ *
+ * The Initial Developer of this code under the NPL is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
+ * Reserved.
+ */
+
+#include "nsISupports.idl"
+#include "nsIURL.idl"
+
+interface nsIUrlListener;
+interface nsIMsgStatusFeedback;
+
+[scriptable, uuid(6CFFCEB0-CB8C-11d2-8065-006008128C4E)]
+interface nsIMsgMailNewsUrl : nsIURL {
+	///////////////////////////////////////////////////////////////////////////////
+	// Eventually we'd like to push this type of functionality up into nsIURI.
+	// The idea is to allow the "application" (the part of the code which wants to 
+	// run a url in order to perform some action) to register itself as a listener
+	// on url. As a url listener, the app will be informed when the url begins to run
+	// and when the url is finished. 
+	////////////////////////////////////////////////////////////////////////////////
+	void RegisterListener (in nsIUrlListener aUrlListener);
+	void UnRegisterListener (in nsIUrlListener aUrlListener);
+
+	// Eventually these will be removed and replaced with calls to nsIMsgStatusFeedback
+	void SetErrorMessage (in string errorMessage);
+	void GetErrorMessage (out string errorMessage);
+
+	// if you really want to know what the current state of the url is (running or not
+	// running) you should look into becoming a urlListener...
+	void SetUrlState(in boolean runningUrl, in nsresult aStatusCode);
+	void GetUrlState(out boolean runningUrl);
+
+	// the ownership model for msg feedback
+	void SetStatusFeedback(in nsIMsgStatusFeedback aMsgFeedback);
+	void GetStatusFeedback(out nsIMsgStatusFeedback aMsgFeedback); 
+};
+
+//////////////////////////////////////////////////////////////////////////////////
+// This is a very small interface which I'm grouping with the mailnewsUrl interface.
+// Several url types (mailbox, imap, nntp) have urls which can be have URI 
+// equivalents. We want to provide the app the ability to get the URI for the 
+// url. This URI to URL mapping doesn't exist for all mailnews urls...hence I'm
+// grouping it into a separate interface...
+//////////////////////////////////////////////////////////////////////////////////
+
+[scriptable, uuid(02338DD2-E7B9-11d2-8070-006008128C4E)]
+interface nsIMsgUriUrl : nsISupports {
+	void GetURI(out string aURI); 
+};