starts splitting up files

mail-config.nix

@@ -0,0 +1,34 @@
+#  nixos-mailserver: a simple mail server
+#  Copyright (C) 2016  Robin Raymond
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program. If not, see <http://www.gnu.org/licenses/>
+
+{ config, pkgs, ... }:
+
+let
+  domain = "example.com";
+  host_prefix = "mail";
+  login_accounts = [ "user1" "user2" ];
+  vmail_id_start = 5000;
+  vmail_user_name = "vmail";
+  vmail_group_name = "vmail";
+  mail_dir = "/var/vmail";
+  cert_file = "mail-server.crt";
+  key_file = "mail-server.key";
+  enable_imap = true;
+  enable_pop3 = false;
+in
+{
+  imports = [ ./mail-server.nix ];
+}

mail-server.nix

@@ -14,19 +14,8 @@
 #  You should have received a copy of the GNU General Public License
 #  along with this program. If not, see <http://www.gnu.org/licenses/>
 
-let
+{ config, pkgs, ... }:
-  domain = "example.com";
+
-  host_prefix = "mail";
-  login_accounts = [ "user1" "user2" ];
-  vmail_id_start = 5000;
-  vmail_user_name = "vmail";
-  vmail_group_name = "vmail";
-  mail_dir = "/var/vmail";
-  cert_file = "mail-server.crt";
-  key_file = "mail-server.key";
-  enable_imap = true;
-  enable_pop3 = false;
-in
 let
   dovecot_maildir = "maildir:" + mail_dir + "/%d/%n/";
   vmail_user = [{