Auto-replies not sent to my reply-to campaign configuration

Auto-replies can clutter your inbox when sending an email campaign. In this post, I answer the infamous question:
Why auto-replies (AKA Vacation Responses) are going back to “From Sender” not the “Reply To” configuration?

Auto-responder header samples:

  1. X-Autogenerated
  2. X-Autoreply
  3. X-AutoReply-From
  4. X-Autoreply-Version
  5. X-Autorespond
  6. X-FC-MachineGenerated
  7. X-Mail-Autoreply
  8. X-MS-Exchange-Inbox-Rules-Loop
  9. X-POST-MessageClass
  10. X-Precedence
  11. X-Sender