title: How to set envelope id in MailMessage class in C#?
body: <p>I want to implement automated email delivery tracking and I found out I could do this using the Delivery Status Notification and setting envelope id to track which email has been delivered/not delivered.</p>
  
  <p>However I can't seem to find a way to set the envelope id parameter using the MailMessage class in C#. As I understand this parameter should go in the MAIL FROM header, something like:</p>
  
  <p>MAIL FROM: RET=HDRS ENVID=QQ314159</p>
  
  <p>I tried setting it using message.Headers.Add(), however when I receive the email and inspect its headers I don't see the envelope id in the 'From' header, as it gets it value from the message.From class property and I can't insert anything else than the email address there.</p>
  
  <p>Can't find any information, anybody has some experience with this?</p>