the CAN-SPAM ACT and other international anti-spam laws, every commercial email message you send must contain an “unsubscribe“ link or other mechanism that allows subscribers to remove themselves from your mailing list. But it may happen that even if the unsubscribe link is included in your mailings, some subscribers are not able to find it. As a result, they are likely to hit the “Mark as Spam” button.
So, why is it important to enable the list-unsubscribe header?
Because every time a “frustated” recipient uses that “Mark as Spam” button to unsubscribe your sender reputation is affected.
The list-unsubscribe header comes to help senders reduce spam complaints and improve deliverability. This is possible because, when it is enabled, the process to unsubscribe is simpler and immediate. Recipients will see an Unsubscribe button, or link, they can click if they would like to automatically stop future messages.
The list-unsubscribe header has been widely supported by major software vendors and ISPs, such Microsoft Windows Live, Yahoo! and Google Gmail (selected senders).
i have looked in system plugin/base/boil/ mail.php, mail_dao.php and mail_services.php
but stuffed if i know how to add this lol
the list@host.com needs to be sitemail addy
mailMessage.Headers.Add("List-Unsubscribe", "<mailto:list@host.com?subject=unsubscribe>");