Add ability to disable List-Unsubscribe header
Provide a way to disable List-Unsubscribe headers for transaction emails. Currently Mailgun adds the List-Unsubscribe header for all emails, including transactional emails like password reset notifications and order confirmation emails. This header is intended for mailing lists, not transactional email. Additionally--we want to handle subscription and unsubscribes in our application not in mailgun.
We discovered this header was recently added when troubleshooting a support request from a user who was not receiving password reset notifications and found he had unsubscribed using a link provided by this recently added header. He did not remember clicking unsubscribe and did not intend to unsubscribe. He is the only user in our account who unsubscribed using this mechanism. Thus, for our sample size of 1, 100% of users who clicked the link provided by this header did so accidentally.