https://www.thenewsletterplugin.com/forums/topic/rfc8058-new-email-header-list-unsubscribe-post
rfc8058, new email header: "List-Unsubscribe-Post"
The "List-Unsubcribe" email header is implemented and working. But mail software sometimes fetches URLs in mail header fields, and thereby accidentally
new emailheaderlistunsubscribepost