Made it work

modules/server/email.nix

@@ -0,0 +1,25 @@
+{ ... }: {
+	imports = [
+		(builtins.fetchTarball {
+			url = "https://gitlab.com/simple-nixos-mailserver/nixos-mailserver/-/archive/nixos-25.05/nixos-mailserver-nixos-25.05.tar.gz";
+			sha256 = "0jpp086m839dz6xh6kw5r8iq0cm4nd691zixzy6z11c4z2vf8v85";
+		})
+	];
+
+	mailserver = {
+		enable = true;
+		fqdn = "mail.hahn1.one";
+		domains = [ "hahn1.one" ];
+
+		# A list of all login accounts. To create the password hashes, use
+		# nix-shell -p mkpasswd --run 'mkpasswd -sm bcrypt'
+		loginAccounts = {
+			"jonas@hahn1.one" = {
+				hashedPassword = "$2b$05$aOMZAUvp4p42su99UwQ0FeKPTVKrHBJX1w7IBG9J39rSjSqyT5Y7C";
+				aliases = ["postmaster@hahn1.one" "j@hahn1.one"];
+			};
+		};
+
+		certificateScheme = "acme-nginx";
+	};
+}