Contact form to notify the author of the node
You may try the Privatemsg module.


  Privatemsg allows your site's visitors to send private messages to each other. Perfect for community oriented sites, such as forums and social networking sites. Many additional features are available as separate modules.
  
  Current features
  
  
  send and receive private messages on a site (between multiple recipients)
  threaded conversations (make it easier to keep track of messages and replies)
  search private messages
  tagging and filtering (helps organise conversations)
  user blocking
  e-mail notifications of new messages