Gmail/Yahoo one-click unsubscribe: what the headers must look like (RFC 8058)

Since 2024 Gmail and Yahoo expect bulk senders to support one-click unsubscribe. A footer link is not enough; it’s two headers, signed.

List-Unsubscribe: <https://example.com/u?token=...>, <mailto:unsub@example.com>
List-Unsubscribe-Post: List-Unsubscribe=One-Click

Requirements (RFC 8058):

• at least one https URI in List-Unsubscribe (mailto alone is not one-click);
• List-Unsubscribe-Post: List-Unsubscribe=One-Click exactly;
• your endpoint accepts a POST with that body and unsubscribes without a confirmation page or login;
• the DKIM signature’s h= covers both headers.

Most ESPs (SendGrid, Mailgun, Postmark, SES) add these for marketing streams but not necessarily for transactional/raw sends you route as bulk. Check a real received message (“Show original”).

Free: oneclick-check — paste the raw headers, get pass/fail per requirement. Passing headers don’t guarantee inbox placement.

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Disclosure: I build Oneclickout, a $29 one-time pack that gives the exact per-ESP fix for your headers. Its free check only offers the pack when it confirms the problem on your page. Everything above works without it.