I'm taking this out of nsIMsgFolder. not part of build yet.

mailnews/imap/public/nsIMsgImapMailFolder.idl

@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public
+ * License Version 1.1 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS
+ * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * rights and limitations under the License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation. All
+ * Rights Reserved.
+ *
+ * Contributor(s):
+ */
+
+#include "nsISupports.idl"
+#include "nsIMsgFolder.idl"
+
+[scriptable, uuid(FBFEBE79-C1DD-11d2-8A40-0060B0FC04D2)]
+interface nsIMsgImapMailFolder : nsISupports {
+  void RemoveSubFolder(in nsIMsgFolder folder);
+  void CreateClientSubfolderInfo(in string folderName);
+  void List();
+  attribute boolean verifiedAsOnlineFolder;
+  attribute boolean explicitlyVerify;
+  attribute wchar hierarchyDelimiter;
+  attribute long boxFlags;
+  attribute string onlineName;
+};
+

mailnews/local/public/nsIMsgLocalMailFolder.idl

@@ -0,0 +1,27 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public
+ * License Version 1.1 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS
+ * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * rights and limitations under the License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation. All
+ * Rights Reserved.
+ *
+ * Contributor(s):
+ */
+
+#include "nsISupports.idl"
+
+[scriptable, uuid(27D2DE40-BAF1-11d2-9578-00805F8AC615)]
+interface nsIMsgLocalMailFolder : nsISupports {
+};

mailnews/news/public/nsIMsgNewsFolder.idl

@@ -0,0 +1,32 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public
+ * License Version 1.1 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS
+ * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * rights and limitations under the License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation. All
+ * Rights Reserved.
+ *
+ * Contributor(s):
+ */
+
+#include "nsISupports.idl"
+#include "nsIMsgFolder.idl"
+
+[scriptable, uuid(3716abe4-f6d4-11d2-86d5-004005263078)]
+interface nsIMsgNewsFolder : nsISupports {
+  attribute string unreadSetStr;
+  attribute string groupUsername;
+  attribute string groupPassword;
+  nsIMsgFolder addNewsgroup(in string newsgroupName, in string setStr);
+};