Scope overlays and modules to specific host sets

modules/services/mail/default.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, self, ... }:
 
 let
   cfg = config.modules.services.mail;
@@ -22,6 +22,10 @@ in {
     };
   };
 
+  imports = [
+    self.inputs.nixos-mailserver.nixosModule
+  ];
+
   config = lib.mkIf cfg.enable {
     services.roundcube = {
       enable = true;