List-Unsubscribe
An email header that gives recipients a one-click way to unsubscribe, now required by Gmail and Yahoo for bulk senders.
List-Unsubscribe is an email header (RFC 2369) that lets the recipient's mail client expose a built-in unsubscribe button. The newer one-click variant (RFC 8058) adds `List-Unsubscribe-Post: List-Unsubscribe=One-Click` and lets the mail client POST to the unsubscribe URL with no further user interaction. Since February 2024, Gmail and Yahoo require one-click List-Unsubscribe on bulk mail (5,000+ messages per day to their users), alongside aligned DKIM and DMARC. Missing or broken List-Unsubscribe is now a top cause of inbox loss.