title: Set Regarding field of email activity in a workflow to the Primary entity
body: <p>Is there a way to set the "Regarding" field for an email in a Send Email activity in a workflow to the Primary entity of the workflow?</p>
  
  <p>I tried using the Form Assistant but it won't let me bind the primary entity of the workflow to the 
  Regarding field of the email message.</p>
  
  <p>Is there a way to accomplish this?</p>