```ruby
require Rails.root.join("config/smtp")

Rails.application.configure do
  config.cache_classes = false
  config.eager_load = false
  config.consider_all_requests_local       = true
  config.action_controller.perform_caching = false
  config.action_mailer.raise_delivery_errors = false
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {:address => 'localhost', :port => 25}
  config.active_support.deprecation = :log
  config.active_record.migration_error = :page_load
  config.assets.debug = true
  config.assets.digest = true
  config.assets.raise_runtime_errors = true
  config.action_view.raise_on_missing_translations = true
  config.action_mailer.default_url_options = { host: ENV.fetch("APPLICATION_HOST") }
end
```

Remove obsolete reference to config for MailGun
user
```ruby
Rails.application.configure do
  config.cache_classes = false
  config.eager_load = false
  config.consider_all_requests_local       = true
  config.action_controller.perform_caching = false
  config.action_mailer.raise_delivery_errors = false
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {:address => 'localhost', :port => 25}
  config.active_support.deprecation = :log
  config.active_record.migration_error = :page_load
  config.assets.debug = true
  config.assets.digest = true
  config.assets.raise_runtime_errors = true
  config.action_view.raise_on_missing_translations = true
  config.action_mailer.default_url_options = { host: ENV.fetch("APPLICATION_HOST") }
end
```
assistant