List-Unsubscribe header for gmail

Hi,

In order to prevent gmail users to have to get their digest or email confrmation from the spam folder, adding List-Unsubscribe header would be great.

https://support.google.com/mail/answer/81126?hl=en#unsub

http://marketingland.com/everything-need-know-gmails-auto-unsubscribe-75605

https://ww.wp.xz.cn/plugins/simple-subscribe/