Method and systems are disclosed for providing a function as a service for an application. The application may comprise an email application. A user may define or select an application codes set for performing a specific functionality. The user may define rules that associate specific events with execution of the application code set. Upon detection of an event, a condition may be checked associated with the application. If the condition is satisfied, the application code set may be caused to be executed. The application code set may modify data, such as an email message.