title: Set the category of an email using custom Outlook Web App Addin
body: <p>I have a scenario where my Outlook Web App Add-in looks for the same email by subject in a database through API. If this email found in the database, I want to mark that email with some categorization so that user can visualize which emails have already been in the Database.</p>
  
  <p>I am using the Office.js to get the subject and pass it to the API as through ajax call. The API written in C# looks into the database and return true or false. 
  if it returns true, I want to mark this email with category red from the code automatically.</p>
  
  <blockquote>
    <p>Red category means follows.</p>
  </blockquote>
  
  <p><a href="https://i.stack.imgur.com/CJWH4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CJWH4.png" alt="enter image description here"></a></p>