hosts/mail-2: enable IPv6 in docker

hosts/mail-2/mailcow.nix

@@ -1,10 +1,20 @@
 { pkgs, ... }:
 
 {
-  virtualisation.docker.enable = true;
+  virtualisation.docker = {
+    enable = true;
+    daemon.settings = {
+      # make sure IPv6 is enabled, else there will be long loading times everywhere
+      ipv6 = true;
+      fixed-cidr-v6 = "fd00:dead:beef:c0::/80";
+      experimental = true;
+      ip6tables = true;
+    };
+  };
 
   environment.systemPackages = with pkgs;  [
     docker-compose
     openssl
   ];
+
 }