diff --git a/config/description.exs b/config/description.exs
index 3abcc6266..52f7d2017 100644
--- a/config/description.exs
+++ b/config/description.exs
@@ -238,7 +238,8 @@ config :pleroma, :config_description, [
           Swoosh.Adapters.AmazonSES,
           Swoosh.Adapters.Dyn,
           Swoosh.Adapters.SocketLabs,
-          Swoosh.Adapters.Gmail
+          Swoosh.Adapters.Gmail,
+          Swoosh.Adapters.Local
         ]
       },
       %{
@@ -449,6 +450,26 @@ config :pleroma, :config_description, [
       }
     ]
   },
+  %{
+    group: :swoosh,
+    type: :group,
+    description: "`Swoosh.Adapters.Local` adapter specific settings",
+    children: [
+      %{
+        group: {:subgroup, Swoosh.Adapters.Local},
+        key: :serve_mailbox,
+        type: :boolean,
+        description: "Run the preview server together as part of your app"
+      },
+      %{
+        group: {:subgroup, Swoosh.Adapters.Local},
+        key: :preview_port,
+        type: :integer,
+        description: "The preview server port",
+        suggestions: [4001]
+      }
+    ]
+  },
   %{
     group: :pleroma,
     key: :uri_schemes,
diff --git a/lib/pleroma/docs/generator.ex b/lib/pleroma/docs/generator.ex
index b57e47e8b..6b12dcdd9 100644
--- a/lib/pleroma/docs/generator.ex
+++ b/lib/pleroma/docs/generator.ex
@@ -58,15 +58,23 @@ defmodule Pleroma.Docs.Generator do
     entity
     |> Map.put(:suggestions, format_suggestions(suggestions))
     |> format_key()
+    |> format_group()
     |> format_children()
   end
 
   defp format_child(entity) do
     entity
     |> format_key()
+    |> format_group()
     |> format_children()
   end
 
+  defp format_group(%{group: group} = entity) do
+    Map.put(entity, :group, format_suggestion(group))
+  end
+
+  defp format_group(entity), do: entity
+
   defp atom_to_string(entity) when is_binary(entity), do: entity
 
   defp atom_to_string(entity) when is_atom(entity), do: inspect(entity)
diff --git a/test/docs/generator_test.exs b/test/docs/generator_test.exs
index 42e7c32c8..0106809c2 100644
--- a/test/docs/generator_test.exs
+++ b/test/docs/generator_test.exs
@@ -207,5 +207,12 @@ defmodule Pleroma.Docs.GeneratorTest do
       child = Enum.at(children, 7)
       assert child[:key] == "application/xml"
     end
+
+    test "subgroup with module name" do
+      [%{children: children} | _] = Generator.convert_to_strings(@descriptions)
+
+      %{group: subgroup} = Enum.at(children, 6)
+      assert subgroup == {":subgroup", "Swoosh.Adapters.SMTP"}
+    end
   end
 end