title: How to create Apple mail plugin
body: <p>I'm going to create a mail plugin for the OS X Mail.app application for some additional features.</p>
  
  <p>I have no idea where to start as there is no official documentation for  plugins.</p>
  
  <p>Can anyone please help me, how can I start the project.
  Is there any initial link or tutorial, please suggest?</p>