[AdrianoKF]

There's also RFC 8058 [0] that proposes to refine the `List-Unsubscribe` header for one-click unsubscriptions. It uses the `List-Unsubscribe-Post` header to indicate that an HTTP POST request can be used to unsubscribe with a single click.

It specifically mentions in section 3.2 that mail receivers are not to crawl this URL without user consent:

> The mail receiver MUST NOT perform a POST on the HTTPS URI without user consent. When and how the user consent is obtained is not part of this specification.

I haven't seen any statistics on how widespread adoption of this RFC is among the major mail providers, though.

[0]: https://datatracker.ietf.org/doc/html/rfc8058