diff --git a/nixos/amon/configuration.nix b/nixos/amon/configuration.nix
index acf5555..a763708 100644
--- a/nixos/amon/configuration.nix
+++ b/nixos/amon/configuration.nix
@@ -105,6 +105,9 @@
     destination $(relay_domains) {
       deliver_to &remote_queue
     }
+    default_destination {
+      reject 550 5.1.1 "We do not relay for this domain"
+    }
   }
   
   smtp tcp://0.0.0.0:25 {