mailserver: Set up DNS recursor

modules/mailserver.nix

@@ -342,5 +342,20 @@ in
           lda_mailbox_autocreate = yes
         '';
       };
+
+    # DNS (recursor for DNSBLs etc.)
+    services.resolved.enable = false;
+    services.unbound = {
+      enable = true;
+      settings = {
+        server = {
+          interface = [ "127.0.0.53" ];
+        };
+      };
+      resolveLocalQueries = false; # does not work with .53
+    };
+    networking.resolvconf.extraConfig = ''
+      name_servers='127.0.0.53'
+    '';
   };
 }