```ruby
Rails.application.configure do
  config.action_mailer.smtp_settings = {
    user_name: ENV['SMTP_USERNAME'],
    password: ENV['SMTP_PASSWORD'],
    address: ENV['SMTP_HOSTNAME'],
    port: ENV['SMTP_PORT'],
    domain: ENV['SMTP_DOMAIN'],
    authentication: :login,
    enable_starttls_auto: true
  }

  config.cache_classes = true
  config.eager_load = true
  config.consider_all_requests_local       = false
  config.action_controller.perform_caching = true
  config.serve_static_files = ENV['RAILS_SERVE_STATIC_FILES'].present?
  config.assets.js_compressor = :uglifier
  config.assets.compile = false
  config.assets.digest = true
  config.log_level = :info
  config.i18n.fallbacks = true
  config.active_support.deprecation = :notify
  config.log_formatter = ::Logger::Formatter.new
  config.active_record.dump_schema_after_migration = false

  config.lograge.formatter = Lograge::Formatters::Logstash.new
  config.lograge.logger = ActiveSupport::Logger.new \
    "#{Rails.root}/log/logstash_#{Rails.env}.json"

  config.mx_checker = MxChecker.new

  config.active_job.queue_adapter = :sidekiq
end
```

Fix host header poison attack
user
```ruby
Rails.application.configure do
  config.action_mailer.smtp_settings = {
    user_name: ENV['SMTP_USERNAME'],
    password: ENV['SMTP_PASSWORD'],
    address: ENV['SMTP_HOSTNAME'],
    port: ENV['SMTP_PORT'],
    domain: ENV['SMTP_DOMAIN'],
    authentication: :login,
    enable_starttls_auto: true
  }

  config.cache_classes = true
  config.eager_load = true
  config.consider_all_requests_local       = false
  config.action_controller.perform_caching = true
  config.serve_static_files = ENV['RAILS_SERVE_STATIC_FILES'].present?
  config.assets.js_compressor = :uglifier
  config.assets.compile = false
  config.assets.digest = true
  config.log_level = :info
  config.i18n.fallbacks = true
  config.active_support.deprecation = :notify
  config.log_formatter = ::Logger::Formatter.new
  config.active_record.dump_schema_after_migration = false

  config.lograge.formatter = Lograge::Formatters::Logstash.new
  config.lograge.logger = ActiveSupport::Logger.new \
    "#{Rails.root}/log/logstash_#{Rails.env}.json"

  config.mx_checker = MxChecker.new

  config.active_job.queue_adapter = :sidekiq

  service_url = URI.parse(ENV.fetch('STAFF_SERVICE_URL'))

  config.action_controller.default_url_options = { host: service_url.hostname }
  config.action_controller.asset_host = service_url.hostname
end
```
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