diff --git a/mailnews/extensions/smime/public/nsIEncryptedSMIMEURIsService.idl b/mailnews/extensions/smime/public/nsIEncryptedSMIMEURIsService.idl
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/mailnews/extensions/smime/src/nsEncryptedSMIMEURIsService.cpp b/mailnews/extensions/smime/src/nsEncryptedSMIMEURIsService.cpp
new file mode 100644
index 00000000000..4867a86a990
--- /dev/null
+++ b/mailnews/extensions/smime/src/nsEncryptedSMIMEURIsService.cpp
@@ -0,0 +1,72 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla 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/MPL/
+ *
+ * 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 Communicator.
+ *
+ * The Initial Developer of the Original Code is
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 2002
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#include "nsEncryptedSMIMEURIsService.h"
+#include "nsString.h"
+#include "nsReadableUtils.h"
+
+
+NS_IMPL_ISUPPORTS1(nsEncryptedSMIMEURIsService, nsIEncryptedSMIMEURIsService)
+
+nsEncryptedSMIMEURIsService::nsEncryptedSMIMEURIsService()
+{
+  NS_INIT_ISUPPORTS();
+}
+
+nsEncryptedSMIMEURIsService::~nsEncryptedSMIMEURIsService()
+{
+}
+
+NS_IMETHODIMP nsEncryptedSMIMEURIsService::RememberEncrypted(const nsACString & uri)
+{
+  // Assuming duplicates are allowed.
+  mEncryptedURIs.AppendCString(nsCString(uri));
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsEncryptedSMIMEURIsService::ForgetEncrypted(const nsACString & uri)
+{
+  // Assuming, this will only remove one copy of the string, if the array
+  // contains multiple copies of the same string.
+  mEncryptedURIs.RemoveCString(nsCString(uri));
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsEncryptedSMIMEURIsService::IsEncrypted(const nsACString & uri, PRBool *_retval)
+{
+  *_retval = (mEncryptedURIs.IndexOf(nsCString(uri)) != -1);
+  return NS_OK;
+}
diff --git a/mailnews/extensions/smime/src/nsEncryptedSMIMEURIsService.h b/mailnews/extensions/smime/src/nsEncryptedSMIMEURIsService.h
new file mode 100644
index 00000000000..d35779fa698
--- /dev/null
+++ b/mailnews/extensions/smime/src/nsEncryptedSMIMEURIsService.h
@@ -0,0 +1,56 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla 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/MPL/
+ *
+ * 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 Communicator.
+ *
+ * The Initial Developer of the Original Code is
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 2002
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef _nsEncryptedSMIMEURIsService_H_
+#define _nsEncryptedSMIMEURIsService_H_
+
+#include "nsIEncryptedSMIMEURIsService.h"
+#include "nsVoidArray.h"
+
+class nsEncryptedSMIMEURIsService : public nsIEncryptedSMIMEURIsService
+{
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIENCRYPTEDSMIMEURISSERVICE
+
+  nsEncryptedSMIMEURIsService();
+  virtual ~nsEncryptedSMIMEURIsService();
+
+protected:
+  nsCStringArray mEncryptedURIs;
+};
+
+#endif