The List-Unsubscribe header is a standard email header (RFC 2369) that gives mailbox providers a URL or mailto address for opting out of a mailing. The related List-Unsubscribe-Post header (RFC 8058) enables true one-click unsubscribe.
Why it matters
Providers use it to show an Unsubscribe button next to the sender name. Recipients who cannot find a button often click Report Spam instead, which damages sender reputation. Large providers have made one-click support a condition for bulk senders, so it is now close to mandatory for high-volume marketing mail. It supplements, and does not replace, the visible unsubscribe link in the body required by laws such as CAN-SPAM.
Example
List-Unsubscribe: <https://example.com/u/abc123>, <mailto:unsub@example.com?subject=unsubscribe>
List-Unsubscribe-Post: List-Unsubscribe=One-ClickWith one-click, the provider sends an HTTP POST to the URL and the request must unsubscribe the person without further steps or a login. The header should be covered by the DKIM signature.
Common mistakes
- Requiring a login or confirmation page after the one-click request.
- Leaving the header out of transactional mail where it is not needed, but adding it to marketing mail without honouring it.
- Taking days to process opt-outs; process them promptly.
Related
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