def notify(contact_request)
      @contact_request = contact_request

      mail to: notification_recipients,
           from: notification_sender(contact_request),
           subject: notification_subject
    end
def notify(contact_request)
      @contact_request = contact_request

      mail to: notification_recipients,
           from: notification_sender(contact_request),
           subject: notification_subject
    end
Subject can be set in your I18n file at config/locales/en.yml
 with the following lookup:

   en.contact_request_mailer.notify.subject