List-Unsubscribe Header Builder (RFC 8058)
Build List-Unsubscribe and one-click List-Unsubscribe-Post headers from a mailto and/or URL.
About this tool
Builds the List-Unsubscribe and List-Unsubscribe-Post email headers for one-click unsubscribe per RFC 8058. Enter a mailto address, an HTTPS unsubscribe URL, and an optional subject, and the tool assembles the correct header lines and reminds you of the Gmail/Yahoo 2024 bulk-sender rules. Useful for email developers and deliverability engineers.
Frequently asked questions
How do I add a one-click unsubscribe header?
Provide an HTTPS url= and the tool emits both List-Unsubscribe: <https://...> and List-Unsubscribe-Post: List-Unsubscribe=One-Click, which is the RFC 8058 one-click pair.
Do I need both a mailto and a URL?
No, either works for a basic List-Unsubscribe, but Gmail and Yahoo one-click requires the HTTPS URL plus the List-Unsubscribe-Post line. Including both a mailto and URL is recommended.
What do Gmail and Yahoo require in 2024?
Bulk senders (5,000+ messages/day) must support one-click unsubscribe (RFC 8058), honour it within two days, and pass SPF, DKIM and DMARC authentication.