fix: remove extra msmtp stanza

rossby/default.nix

@@ -94,7 +94,7 @@ let
       };
       cachix.enable = false;
       monitoring.nodeExporter.enable = false;
-      mft.enable = true; # Mellanox MFT
+      mft.enable = false; # Mellanox MFT
     };
 
     networking = {
@@ -289,6 +289,18 @@ let
             permissions = "u+rs,g+rx,o+rx";
         };
     };
+
+    # Use nvd to get package diff before apply
+    system.activationScripts.system-diff = {
+     supportsDryActivation = true; # safe: only outputs to stdout
+     text = ''
+       export PATH="${pkgs.lib.makeBinPath [ pkgs.nixVersions.latest ]}:$PATH"
+       if [ -e /run/current-system ]; then
+         ${pkgs.lib.getExe pkgs.nvd} diff '/run/current-system' "$systemConfig" || true
+       fi
+     '';
+    };
+
   };
 
   openssh-shosts = pkgs.openssh.overrideAttrs (attrs: {