Why It Matters
Since June 2024, Google and Yahoo require bulk senders (those sending over 5,000 emails per day) to support one-click List-Unsubscribe. If you don't include it, your emails may be blocked or filtered to spam. But even beyond compliance, List-Unsubscribe is good for you. When recipients can easily unsubscribe via the header, they're less likely to hit the spam button — and spam complaints hurt your reputation far more than unsubscribes do.
How It Works
You add two headers to your outgoing emails: List-Unsubscribe (containing a mailto: address and/or an HTTPS URL) and List-Unsubscribe-Post (which enables one-click functionality via an HTTP POST request). When a recipient clicks the unsubscribe button shown by their email client, the client sends a POST request to your URL, and you process the removal. The whole thing happens without the subscriber leaving their inbox. Most ESPs handle these headers automatically.
Quick Tips
- Include both a mailto: and an HTTPS URL in your List-Unsubscribe header — different clients use different methods
- Process List-Unsubscribe requests instantly; delayed processing means you're still emailing someone who already opted out
- Check that your ESP is adding the
List-Unsubscribe-Post: List-Unsubscribe=One-Clickheader — without it, the one-click requirement isn't met