Add Rupert’s configuration

options/email.nix

@@ -0,0 +1,28 @@
+{ config, lib, ... }:
+with lib;
+{
+    options.email = {
+        fromAddress = mkOption {
+            type = types.str;
+            example = "noreply@example.com";
+            description = ''
+                E-Mail address automated e-mails are sent from.
+            '';
+        };
+        fromIdentity = mkOption {
+            type = types.str;
+            default = "${config.networking.hostName} <${config.email.fromAddress}>";
+            example = "Maintenance (no reply) <noreply@example.com>";
+            description = ''
+                E-Mail identity automated e-mails are sent from.
+            '';
+        };
+        adminEmail = mkOption {
+            type = types.str;
+            example = "admin@example.com";
+            description = ''
+                E-Mail address automated e-mails are sent to.
+            '';
+        };
+    };
+}