A mailing list is a list of email address.
The users:
The list is stored as an alias (ie an alias has one or many addresses listed).
When an email is sent to the mailing list:
A mechanism should be provided to be able to unsubscribe.
To unsubscribe, the user needs to:
List-Unsubscribe: <https://www.example.com/email-unsubscribe?listid=xxxx>