config/initializers/email.yml（Production環境時のSMTP設定）

email.rb

if Rails.env == "production"
  filename = File.join(File.dirname(__FILE__), '..', 'email.yml')

  if File.file?(filename)
    config = YAML::load_file(filename)

    if config.is_a?(Hash) && config.has_key?(Rails.env)
      config[Rails.env].each do |k, v|
        v.symbolize_keys! if v.respond_to?(:symbolize_keys!)
        ActionMailer::Base.send("#{k}=", v)
      end
    end
  end
end