diff --git a/plugins/libkolab/lib/kolab_format_configuration.php b/plugins/libkolab/lib/kolab_format_configuration.php
index 17b46a70..4506ed3c 100644
--- a/plugins/libkolab/lib/kolab_format_configuration.php
+++ b/plugins/libkolab/lib/kolab_format_configuration.php
@@ -241,6 +241,10 @@ class kolab_format_configuration extends kolab_format
             else if (!empty($member['params']['message-id'])) {
                 $words[] = $member['params']['message-id'];
             }
+            else {
+                // derive message identifier from URI
+                $words[] = md5($url);
+            }
         }
 
         return $words;
diff --git a/plugins/libkolab/lib/kolab_storage_config.php b/plugins/libkolab/lib/kolab_storage_config.php
index e04ccd68..22fb90c3 100644
--- a/plugins/libkolab/lib/kolab_storage_config.php
+++ b/plugins/libkolab/lib/kolab_storage_config.php
@@ -351,6 +351,8 @@ class kolab_storage_config
                 'params' => $params,
             );
         }
+
+        return false;
     }
 
     /**
@@ -765,10 +767,16 @@ class kolab_storage_config
         $filter  = array(
             array('type', '=', 'relation'),
             array('category', '=', 'generic'),
-            // @TODO: what if Message-Id (and Date) does not exist?
-            array('member', '=', $message->get('message-id', false)),
         );
 
+        // query by message-id
+        $member_id = $message->get('message-id', false);
+        if (empty($member_id)) {
+            // derive message identifier from URI
+            $member_id = md5($uri);
+        }
+        array('member', '=', $member_id);
+
         // get UIDs of assigned notes
         foreach ($this->get_objects($filter, $default) as $relation) {
             // we don't need to update members if the URI is found