diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index faf6846e4b6fde4cb62b75de049381984bf3c406..f007d11c729c8ff517ea36e60e9d8f52da6517cb 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Fix displaying mailer previews on non local requests when config
+    `action_mailer.show_previews` is set
+
+    *Wojciech Wnętrzak*
+
 *   `rails server` will now honour the `PORT` environment variable
 
     *David Cornu*
diff --git a/railties/lib/rails/mailers_controller.rb b/railties/lib/rails/mailers_controller.rb
index 78a857e0f16bcb1d5f07c95ac3f6e260ddf6c1f8..ed0ea9dd4d4ae3bc581fc8de33c1db10f30e7ef1 100644
--- a/railties/lib/rails/mailers_controller.rb
+++ b/railties/lib/rails/mailers_controller.rb
@@ -3,7 +3,7 @@
 class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugExceptions::RESCUES_TEMPLATE_PATH
 
-  before_action :require_local!
+  before_action :require_local!, unless: :show_previews?
   before_action :find_preview, only: :preview
 
   def index
@@ -41,6 +41,10 @@ def preview
   end
 
   protected
+    def show_previews?
+      ActionMailer::Base.show_previews
+    end
+
     def find_preview
       candidates = []
       params[:path].to_s.scan(%r{/|$}){ candidates << $` }
diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index e462d2c15e3b3f798b6288d81c6f92ac8c58f575..643d876a263824790c8556bcad0f41e3a7d0cdbc 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -31,7 +31,7 @@ def teardown
     test "/rails/mailers is accessible with correct configuraiton" do
       add_to_config "config.action_mailer.show_previews = true"
       app("production")
-      get "/rails/mailers"
+      get "/rails/mailers", {}, {"REMOTE_ADDR" => "4.2.42.42"}
       assert_equal 200, last_response.status
     end