6. Keyword di gestione delle sottoscrizioni

6.1. $canunsubscribe

6.2. $unsubscribed

$canunsubscribe indicates that a message contains a valid List-Unsubscribe header compliant with [RFC8058] and suitable for one-click unsubscribe functionality after server-side validation. This lets clients offer unsubscribe UI without fetching and validating the header for every message.

$unsubscribed records that the user attempted to unsubscribe from the mailing list associated with a message. It is set by a client after an unsubscribe attempt and MUST NOT be set if the attempt definitely failed. Clients can use it to remind users that they have already tried to unsubscribe from a sender or list.