diff --git a/nix/modules/nixos/infrastructure/mailserver/default.nix b/nix/modules/nixos/infrastructure/mailserver/default.nix
index 19642ba..41afd19 100644
--- a/nix/modules/nixos/infrastructure/mailserver/default.nix
+++ b/nix/modules/nixos/infrastructure/mailserver/default.nix
@@ -1,12 +1,84 @@
 {
   config,
   lib,
-  inputs,
+  pkgs,
   ...
 }:
 let
   cfg = config.khscodes.infrastructure.mailserver;
   fqdn = config.khscodes.networking.fqdn;
+  adminCredentialsFile = "/etc/stalwart/admin-pw";
+  stalwart-spam-filter = pkgs.callPackage ./stalwart-spam-filter.nix { };
+  ifthen = condition: expr: {
+    "if" = condition;
+    "then" = expr;
+  };
+  otherwise = expr: { "else" = expr; };
+  authDkimForDomain = domain: [
+    (ifthen "sender_domain = '${domain}'" "['${domain}_rsa', '${domain}_ed25519']")
+  ];
+  authDkim = lib.lists.flatten (lib.lists.map authDkimForDomain cfg.domains);
+  signatureForDomain = domain: [
+    {
+      name = "${domain}_rsa";
+      value = {
+        inherit domain;
+        private-key = "%{file:/run/secret/dkim/${domain}.snm_rsa.key}";
+        selector = "snm_rsa";
+        headers = [
+          "From"
+          "To"
+          "Cc"
+          "Date"
+          "Subject"
+          "Message-ID"
+          "Organization"
+          "MIME-Version"
+          "Content-Type"
+          "In-Reply-To"
+          "References"
+          "List-Id"
+          "User-Agent"
+          "Thread-Topic"
+          "Thread-Index"
+        ];
+        algorithm = "rsa-sha256";
+        canonicalization = "relaxed/relaxed";
+        report = true;
+      };
+    }
+    {
+      name = "${domain}_ed25519";
+      value = {
+        inherit domain;
+        private-key = "%{file:/run/secret/dkim/${domain}.snm_ed25519.key}";
+        selector = "snm_ed25519";
+        headers = [
+          "From"
+          "To"
+          "Cc"
+          "Date"
+          "Subject"
+          "Message-ID"
+          "Organization"
+          "MIME-Version"
+          "Content-Type"
+          "In-Reply-To"
+          "References"
+          "List-Id"
+          "User-Agent"
+          "Thread-Topic"
+          "Thread-Index"
+        ];
+        algorithm = "ed25519-sha256";
+        canonicalization = "relaxed/relaxed";
+        report = true;
+      };
+    }
+  ];
+  dkimSignatures = {
+    signature = lib.listToAttrs (lib.lists.flatten (lib.lists.map signatureForDomain cfg.domains));
+  };
 in
 {
   options.khscodes.infrastructure.mailserver = {
@@ -18,7 +90,6 @@ in
   };
   imports = [
     ./dkim.nix
-    inputs.simple-nixos-mailserver.nixosModules.mailserver
   ];
   config = lib.mkIf cfg.enable {
     # TODO: Include a similiar rule for openstack
@@ -49,43 +120,87 @@ in
         }
       )
     ];
-    mailserver = {
-      enable = true;
-      certificateScheme = "acme";
-      fqdn = config.khscodes.networking.fqdn;
-      domains = cfg.domains;
+    environment.etc."stalwart/admin-pw".text = "test";
+    networking.firewall.allowedTCPPorts = [
+      25
+      465
+      993
+    ];
+    security.acme.certs."${fqdn}" = {
+      # Not sure if this does an actual reload (which is not supported apparently),
+      # or if it does a full restart (which would be needed).
+      # If it doesn't work, then I should look into using post run to query the API.
+      reloadServices = [ "stalwart-mail.service" ];
     };
-    services.prometheus.exporters.postfix = {
-      enable = true;
+    users.users.stalwart-mail.extraGroups = [ config.security.acme.certs.${fqdn}.group ];
+    systemd.services.stalwart-mail = {
+      serviceConfig = {
+        ReadOnlyPaths = [ config.security.acme.certs."${fqdn}".directory ];
+      };
+      wants = [ "acme-${fqdn}.service" ];
+      after = [ "acme-${fqdn}.service" ];
     };
-    khscodes.infrastructure.vault-prometheus-sender.exporters.enabled = [ "postfix" ];
-    services.fail2ban.jails = {
-      postfix = {
-        settings = {
-          enabled = true;
-          mode = "aggressive";
-          port = "smtp,submission,imap,imaps,pop3,pop3s";
-          findtime = 600;
-          bantime = "1d";
-          maxretry = 3;
+    services.stalwart-mail = {
+      enable = true;
+      package = pkgs.stalwart-mail;
+      openFirewall = false;
+      settings = {
+        http = {
+          url = "https://${fqdn}";
+          use-x-forwarded = true;
         };
-      };
-      dovecot = {
-        settings = {
-          enabled = true;
-          mode = "aggressive";
-          findtime = 600;
-          bantime = "1d";
-          maxretry = 3;
+        server = {
+          hostname = fqdn;
+          tls = {
+            enable = true;
+            certificate = "default";
+            implicit = true;
+            ignore-client-order = true;
+          };
+          listener = {
+            smtp = {
+              protocol = "smtp";
+              bind = "[::]:25";
+            };
+            submissions = {
+              bind = "[::]:465";
+              protocol = "smtp";
+            };
+            imaps = {
+              bind = "[::]:993";
+              protocol = "imap";
+            };
+            management = {
+              bind = [ "127.0.0.1:8080" ];
+              protocol = "http";
+            };
+          };
         };
-      };
-      roundcube-auth = {
-        settings = {
-          enabled = true;
-          findtime = 600;
-          maxretry = 7;
+        # There's a bug in 25.05 that references the wrong file. Fixed in master/unstable.
+        spam-filter.resource = "file://${stalwart-spam-filter}/spam-filter.toml";
+        authentication.fallback-admin = {
+          user = "admin";
+          secret = "%{file:/etc/stalwart/admin-pw}%";
         };
-      };
+        certificate.default = {
+          cert = "%{file://${config.security.acme.certs."${fqdn}".directory}/fullchain.pem}";
+          private-key = "%{file://${config.security.acme.certs."${fqdn}".directory}/key.pem}";
+          default = true;
+        };
+        auth.dkim = {
+          sign = authDkim ++ [
+            (otherwise false)
+          ];
+        };
+        directory.memory = {
+          type = "memory";
+          domains = [
+            "agerlinskovgaard.dk"
+            "agerlin-skovgaard.dk"
+          ];
+        };
+      }
+      // dkimSignatures;
     };
   };
 }
diff --git a/nix/modules/nixos/infrastructure/mailserver/dkim.nix b/nix/modules/nixos/infrastructure/mailserver/dkim.nix
index 5f27112..d32fd0f 100644
--- a/nix/modules/nixos/infrastructure/mailserver/dkim.nix
+++ b/nix/modules/nixos/infrastructure/mailserver/dkim.nix
@@ -52,25 +52,35 @@ in
     };
   };
   config = lib.mkIf (cfg.enable) {
-    mailserver = {
-      dkimSigning = false;
-    };
-    services.rspamd.locals."dkim_signing.conf" = lib.mkForce {
-      text = ''
-        enabled = true;
-        domain {
-          ${lib.strings.concatStringsSep "\n " (lib.lists.map dkimSigningForDomain cfg.domains)}
-        }
-      '';
-    };
-    systemd.services.rspamd = {
+    # mailserver = {
+    #   dkimSigning = false;
+    # };
+    # services.rspamd.locals."dkim_signing.conf" = lib.mkForce {
+    #   text = ''
+    #     enabled = true;
+    #     domain {
+    #       ${lib.strings.concatStringsSep "\n " (lib.lists.map dkimSigningForDomain cfg.domains)}
+    #     }
+    #   '';
+    # };
+    # systemd.services.rspamd = {
+    #   unitConfig = {
+    #     ConditionPathExists = domainKeyPaths;
+    #   };
+    # };
+    # systemd.services.postfix = {
+    #   unitConfig = {
+    #     ConditionPathExists = domainKeyPaths;
+    #   };
+    # };
+    systemd.services.stalwart-mail = {
       unitConfig = {
         ConditionPathExists = domainKeyPaths;
       };
-    };
-    systemd.services.postfix = {
-      unitConfig = {
-        ConditionPathExists = domainKeyPaths;
+      serviceConfig = {
+        ReadOnlyPaths = [
+          "/run/secret/dkim"
+        ];
       };
     };
     khscodes.infrastructure.vault-server-approle.policy = {
@@ -121,8 +131,7 @@ in
             }) cfg.domains)
             ++ (lib.lists.map (domain: {
               fqdn = domain;
-              # TODO: Use something here that doesn't require knowing the IP, such that we don't tie this down to hcloud instances.
-              content = ''"v=spf1 ip4:${config.khscodes.hcloud.output.server.compute.ipv4_address} ip6:${config.khscodes.hcloud.output.server.compute.ipv6_address} -all"'';
+              content = ''"v=spf1 mx -all"'';
               ttl = 600;
             }) cfg.domains)
             ++ (lib.lists.map (domain: {
@@ -159,7 +168,11 @@ in
         }
       )
     ];
-
+    systemd.services.stalwart-mail.serviceConfig = {
+      ReadWritePaths = [
+        "/run/secret/dkim"
+      ];
+    };
     khscodes.services.vault-agent.templates = lib.lists.flatten (
       lib.lists.map (domain: [
         {
@@ -170,11 +183,10 @@ in
           '';
           destination = rsaKeyPath domain;
           perms = "0600";
-          owner = "rspamd";
-          group = "rspamd";
+          owner = "stalwart-mail";
+          group = "stalwart-mail";
           restartUnits = [
-            "rspamd.service"
-            "postfix.service"
+            "stalwart-mail.service"
           ];
         }
         {
@@ -185,11 +197,10 @@ in
           '';
           destination = ed25519KeyPath domain;
           perms = "0600";
-          owner = "rspamd";
-          group = "rspamd";
+          owner = "stalwart-mail";
+          group = "stalwart-mail";
           restartUnits = [
-            "rspamd.service"
-            "postfix.service"
+            "stalwart-mail.service"
           ];
         }
       ]) cfg.domains
diff --git a/nix/modules/nixos/infrastructure/mailserver/stalwart-spam-filter.nix b/nix/modules/nixos/infrastructure/mailserver/stalwart-spam-filter.nix
new file mode 100644
index 0000000..d0ca6c6
--- /dev/null
+++ b/nix/modules/nixos/infrastructure/mailserver/stalwart-spam-filter.nix
@@ -0,0 +1,43 @@
+{
+  lib,
+  fetchFromGitHub,
+  stdenv,
+  stalwart-mail,
+  nix-update-script,
+}:
+
+stdenv.mkDerivation (finalAttrs: {
+  pname = "spam-filter";
+  version = "2.0.3";
+
+  src = fetchFromGitHub {
+    owner = "stalwartlabs";
+    repo = "spam-filter";
+    tag = "v${finalAttrs.version}";
+    hash = "sha256-NhD/qUiGhgESwR2IOzAHfDATRlgWMcCktlktvVfDONk=";
+  };
+
+  buildPhase = ''
+    bash ./build.sh
+  '';
+
+  installPhase = ''
+    mkdir -p $out
+    cp spam-filter.toml $out/
+  '';
+
+  passthru = {
+    updateScript = nix-update-script { };
+  };
+
+  meta = {
+    description = "Secure & modern all-in-one mail server Stalwart (spam-filter module)";
+    homepage = "https://github.com/stalwartlabs/spam-filter";
+    changelog = "https://github.com/stalwartlabs/spam-filter/blob/${finalAttrs.src.tag}/CHANGELOG.md";
+    license = with lib.licenses; [
+      mit
+      asl20
+    ];
+    inherit (stalwart-mail.meta) maintainers;
+  };
+})
diff --git a/nix/systems/aarch64-linux/mx.kaareskovgaard.net/default.nix b/nix/systems/aarch64-linux/mx.kaareskovgaard.net/default.nix
index 5904b8b..42ad3a2 100644
--- a/nix/systems/aarch64-linux/mx.kaareskovgaard.net/default.nix
+++ b/nix/systems/aarch64-linux/mx.kaareskovgaard.net/default.nix
@@ -1,5 +1,6 @@
 {
   inputs,
+  config,
   ...
 }:
 {
@@ -9,7 +10,7 @@
   ];
   khscodes.infrastructure.provisioning.pre.modules = [
     (
-      { config, ... }:
+      { ... }:
       {
         khscodes.vault = {
           enable = true;
@@ -22,11 +23,6 @@
             description = "Secrets used for mx.kaareskovgaard.net";
           };
         };
-        resource.hcloud_volume.mail_disk = {
-          name = "mx.kaareskovgaard.net-mail1";
-          size = 20;
-          server_id = config.khscodes.output.server.compute.id;
-        };
       }
     )
   ];
@@ -50,21 +46,41 @@
       };
     };
   };
-  # services.roundcube = {
-  #   enable = true;
-  #   hostName = "mail.kaareskovgaard.net";
-  #   configureNginx = true;
-  #   extraConfig = ''
-  #     # starttls needed for authentication, so the fqdn required to match
-  #     # the certificate
-  #     $config['smtp_host'] = "tls://${config.mailserver.fqdn}";
-  #     $config['smtp_user'] = "%u";
-  #     $config['smtp_pass'] = "%p";
-  #   '';
-  # };
+  services.roundcube = {
+    enable = true;
+    hostName = "mail.kaareskovgaard.net";
+    configureNginx = true;
+    extraConfig = ''
+      # starttls needed for authentication, so the fqdn required to match
+      # the certificate
+      $config['smtp_host'] = "ssl://${config.khscodes.networking.fqdn}:465";
+      $config['imap_host'] = "ssl://${config.khscodes.networking.fqdn}:993";
+    '';
+  };
   khscodes.services.nginx = {
     enable = true;
-    # virtualHosts."mail.kaareskovgaard.net" = { };
+    virtualHosts."mx.kaareskovgaard.net" = {
+      locations."/" = {
+        proxyPass = "http://127.0.0.1:8080";
+        proxyWebsockets = true;
+        recommendedProxySettings = true;
+      };
+    };
+    virtualHosts."mail.kaareskovgaard.net" = { };
+    virtualHosts."autoconfig.kaareskovgaard.net" = {
+      locations."/" = {
+        proxyPass = "http://127.0.0.1:8080";
+        proxyWebsockets = true;
+        recommendedProxySettings = true;
+      };
+    };
+    virtualHosts."autodiscover.kaareskovgaard.net" = {
+      locations."/" = {
+        proxyPass = "http://127.0.0.1:8080";
+        proxyWebsockets = true;
+        recommendedProxySettings = true;
+      };
+    };
   };
   khscodes.networking.fqdn = "mx.kaareskovgaard.net";
   system.stateVersion = "25.05";