config/initializers/disable_mailer_annotations.rb

@@ -0,0 +1,23 @@
+# Disable view annotations for mailer templates to prevent HTML comments
+# from breaking email formatting in development mode
+if Rails.env.development?
+  Rails.application.configure do
+    # Override the annotation setting for ActionMailer specifically
+    config.to_prepare do
+      ActionMailer::Base.prepend(Module.new do
+        def mail(headers = {}, &block)
+          # Temporarily disable view annotations during email rendering
+          original_setting = ActionView::Base.annotate_rendered_view_with_filenames
+          ActionView::Base.annotate_rendered_view_with_filenames = false
+          
+          result = super(headers, &block)
+          
+          # Restore original setting
+          ActionView::Base.annotate_rendered_view_with_filenames = original_setting
+          
+          result
+        end
+      end)
+    end
+  end
+end