The mailto: version of the list-unsubscribe header is automatically injected into the headers of every single email communication sent from Communicator®.
Supported by Microsoft, Google (select senders only) et al, the presence of the list-unsubscribe header enables a button / link in the associated web interfaces. Upon being clicked an email is then sent to the mailto: stipulated in the list-unsubscribe header which in Communicator Corp’s case has an encrypted subject line appended to it (example shown below).
List-Unsubscribe: mailto:[email protected]?subject=List-Unsubscribe:riHaUFi9YW4JIOv45QgB22pLFRQDUbg6532
Upon receipt of the list-unsubscribe email, Communicator Corp decrypts the message’s subject line and unsubscribes the individual from the underlying mailing list.