Add RFC2822 date header

lib/philomena/mailer.ex

@@ -1,9 +1,35 @@
 defmodule Philomena.Mailer do
   use Swoosh.Mailer, otp_app: :philomena
+  alias Swoosh.Email
 
-  @spec deliver_later(Swoosh.Email.t()) :: {:ok, Swoosh.Email.t()}
+  @spec deliver_later(Email.t()) :: {:ok, Email.t()}
   def deliver_later(mail) do
     Task.Supervisor.start_child(Philomena.AsyncEmailSupervisor, fn -> deliver(mail) end)
     {:ok, mail}
   end
+
+  @spec format_message(Email.t()) :: Email.t()
+  def format_message(mail) do
+    mail
+    |> Email.from({"noreply", mailer_address()})
+    |> Email.header("Message-ID", rfc2822_message_id())
+    |> Email.header("Date", rfc2822_date())
+  end
+
+  defp rfc2822_message_id do
+    id =
+      :crypto.strong_rand_bytes(16)
+      |> Base.encode16()
+      |> String.downcase()
+
+    "<#{id}.#{mailer_address()}>"
+  end
+
+  defp rfc2822_date do
+    Calendar.strftime(DateTime.utc_now(), "%a, %-d %b %Y %H:%M:%S %z")
+  end
+
+  defp mailer_address do
+    Application.get_env(:philomena, :mailer_address)
+  end
 end

lib/philomena/users/user_notifier.ex

@@ -5,27 +5,13 @@ defmodule Philomena.Users.UserNotifier do
   defp deliver(to, subject, body) do
     Email.new(
       to: {to, to},
-      from: {"noreply", mailer_address()},
       subject: subject,
       text_body: body
     )
-    |> Email.header("Message-ID", message_id())
+    |> Mailer.format_message()
     |> Mailer.deliver_later()
   end
 
-  defp message_id do
-    id =
-      :crypto.strong_rand_bytes(16)
-      |> Base.encode16()
-      |> String.downcase()
-
-    "<#{id}.#{mailer_address()}>"
-  end
-
-  defp mailer_address do
-    Application.get_env(:philomena, :mailer_address)
-  end
-
   @doc """
   Deliver instructions to confirm account.
   """