   @impl true
   def deliver(%Email{} = email, config \\ []) do
     headers = prepare_headers(config)
-    params = email |> prepare_body |> Swoosh.json_library().encode!
+    params = email |> prepare_body(config) |> Swoosh.json_library().encode!
     url = [base_url(config), api_endpoint(email)]
 
     case Swoosh.ApiClient.post(url, headers, params, email) do

    end
  end

  defp prepare_body(emails) when is_list(emails) do
    Enum.map(emails, &prepare_body/1)
  end

  defp prepare_body(email) do

  @impl true
  def deliver_many(emails, config \\ []) when is_list(emails) do
    headers = prepare_headers(config)
    body = emails |> prepare_body(config) |> Swoosh.json_library().encode!
    url = [base_url(config), api_endpoint(List.first(emails), true)]

    # Could not use `Swoosh.ApiClient.post` here since I have more than one email
