cfg/postfix.nix: factor out from base-medium.nix

I plan to use postfix in a headless system, and base-medium.nix is
desktop oriented at the moment.

Author: bjornfor

cfg/base-medium.nix

@@ -6,6 +6,7 @@
     ./munin.nix
     ./desktop-gnome3.nix
     ./dictionary.nix
+    ./postfix.nix
     ./syncthing.nix
     ./virtualisation.nix
   ];
@@ -189,26 +190,6 @@
     # for hamster-time-tracker
     dbus.packages = with pkgs; [ gnome2.GConf ];
 
-    postfix = {
-      enable = true;
-      # Possibly set "domain" in machine specific configs.
-      # The default "From:" address is
-      #   user@${config.networking.hostName}.localdomain
-      #domain = "server1.example";
-      rootAlias = "[email protected]";
-      extraConfig = ''
-        inet_interfaces = loopback-only
-
-        # Postfix (or my system) seems to prefer ipv6 now, but that breaks on
-        # my network:
-        #
-        #   connect to gmail-smtp-in.l.google.com[2a00:1450:4010:c09::1b]:25: Network is unreachable
-        #
-        # So let's force ipv4.
-        smtp_address_preference = ipv4
-      '';
-    };
-
     # Provide "MODE=666" or "MODE=664 + GROUP=plugdev" for a bunch of USB
     # devices, so that we don't have to run as root.
     udev.packages = with pkgs; [

cfg/postfix.nix

@@ -0,0 +1,23 @@
+{
+  services = {
+    postfix = {
+      enable = true;
+      # Possibly set "domain" in machine specific configs.
+      # The default "From:" address is
+      #   user@${config.networking.hostName}.localdomain
+      #domain = "server1.example";
+      rootAlias = "[email protected]";
+      extraConfig = ''
+        inet_interfaces = loopback-only
+
+        # Postfix (or my system) seems to prefer ipv6 now, but that breaks on
+        # my network:
+        #
+        #   connect to gmail-smtp-in.l.google.com[2a00:1450:4010:c09::1b]:25: Network is unreachable
+        #
+        # So let's force ipv4.
+        smtp_address_preference = ipv4
+      '';
+    };
+  };
+}