One-click unsubscribe
Pairing a List-Unsubscribe header containing an HTTPS URI with a List-Unsubscribe-Post header whose value is exactly `List-Unsubscribe=One-Click`, so a receiver can unsubscribe the reader with a single HTTPS POST. Both headers must be covered by the DKIM signature.
In plain terms
The version of unsubscribe that works in one tap, with no landing page and no confirmation step.
Why it matters for deliverability
It is a hard requirement for bulk senders at the major mailbox providers, and the DKIM-coverage detail is the part most implementations get wrong — an unsigned header does not count.
What to do about it
- Send both List-Unsubscribe and List-Unsubscribe-Post.
- Confirm both headers are inside the DKIM signature's h= list.
- Honour the POST without asking the reader to confirm anything.
- Keep a visible unsubscribe link in the body as well — the header does not replace it.
Source
RFC 8058 — Signaling One-Click Functionality for List Email Headers
“The List-Unsubscribe-Post header MUST contain the single key/value pair "List-Unsubscribe=One-Click".”
Checked 2026-08-29
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