--- a/dnsbl.conf	Thu Oct 04 22:45:21 2007 -0700
+++ b/dnsbl.conf	Sat Oct 06 10:56:35 2007 -0700
@@ -64,6 +64,7 @@
     env_to {
         # !! replace this with your domain names
         # child contexts are not allowed to specify recipient addresses outside these domains
+        # if this is a backup-mx, you need to include here domains for which you relay to the primary mx
         include "/etc/mail/local-host-names";
     };