[Minor] Add composite for suspicios free/disposamail MDN usage

conf/composites.conf

@@ -168,6 +168,13 @@ composites {
     policy = "leave";
     description = "Message exhibits strong characteristics of advance fee fraud (AFF a/k/a '419' spam) involving freemail addresses";
   }
+  SUSPICIOS_MDN {
+    expression = "(FREEMAIL_MDN | DISPOSABLE_MDN) & !(FREEMAIL_FROM | FREEMAIL_ENVFROM)";
+    score = 2.0;
+    policy = "leave";
+    description = "Message delivery notification should go to freemail or disposable e-mail, but message was not sent from a freemail address";
+    group = "scams";
+  }
   REDIRECTOR_URL_ONLY {
     expression = "HFILTER_URL_ONLY & REDIRECTOR_URL";
     score = 1.0;