One-Click Unsubscribe
One-click unsubscribe lets a receiving mail system submit an opt-out through signed message headers. A footer link alone does not implement RFC 8058.
One-click unsubscribe lets a recipient's mail system submit an unsubscribe request without making the recipient complete a form on the sender's website. RFC 8058 defines the mechanism.
How the request works
The sender includes an HTTPS address in List-Unsubscribe and the value List-Unsubscribe=One-Click in List-Unsubscribe-Post. A valid DKIM signature must cover both headers. With user consent, the receiving system sends an HTTPS POST to that address.
The address identifies the recipient and list so the sender can process the request without a login, cookies, or another confirmation. RFC 8058 also prohibits redirecting that POST. Using a POST distinguishes the action from an automated link preview that fetches a page. See the standard's implementation requirements.
Keep the visible unsubscribe link
A footer link and an inbox unsubscribe control are separate implementations. Google's bulk-sender requirements call for one-click unsubscribe for marketing and subscribed messages, plus a clearly visible body link. Its bulk threshold concerns senders of 5,000 or more messages per day to personal Gmail accounts. Check the Google sender guidelines for scope and processing requirements.
Test that a request stops the relevant subscription in subsequent sends, including scheduled messages. Do not assume it cancels every unrelated list or the person's product account.