Level: Intermediate
These two specific headers work together to enable the one-click unsubscribe experience mail clients display, and both need to be correctly formatted for compliance.
List-Unsubscribe Specifies the Method
This header can contain a mailto address, a URL, or both, telling the receiving mail client how an unsubscribe request should be submitted on the recipient's behalf.
List-Unsubscribe-Post Enables the True One-Click Experience
This companion header, containing a specific required value, signals to the mail client that it can submit the unsubscribe request automatically via a POST request without further recipient interaction.
Both Headers Need to Point to a Genuinely Working Endpoint
The URL or address referenced in these headers must actually process the unsubscribe request correctly and promptly, since a technically present but non-functional header doesn't satisfy the underlying compliance intent.
Next step: Use the SeoWolf's Notepad to document the exact header values and endpoint your unsubscribe implementation uses for future reference and troubleshooting.