List-Unsubscribe
Building on from your standard unsubscribe link on the top and/or bottom of your emails, the List-Unsubscribe field is a command in the header of your email. This is to used to help a recipient to unsubscribe easier and for that data to be fed back directly to the Email Service Provider and to the list owner with the vision to make the unsubscription process as simple and efficient as possible.
Here is an example of a List-Unsubscribe Header:
List-Unsubscribe: <mailto:listrequest@example.com?subject=unsubscribe>,<https://example.com/unsubscribe.html?opaque=123456789>