app:update

config/environments/development.rb

@@ -40,6 +40,8 @@ Rails.application.configure do
   # Don't care if the mailer can't send.
   config.action_mailer.raise_delivery_errors = false
 
+  # Disable caching for Action Mailer templates even if Action Controller
+  # caching is enabled.
   config.action_mailer.perform_caching = false
 
   config.action_mailer.default_url_options = { host: "localhost", port: 3000 }