Free QA tool
List-Unsubscribe header builder
Build List-Unsubscribe and List-Unsubscribe-Post header blocks for unsubscribe QA testing.
Generated header block
List-Unsubscribe headers
Copy this block into your email fixture, ESP setting, or QA assertion.
List-Unsubscribe: <mailto:unsubscribe@example.com>, <https://example.com/unsubscribe> List-Unsubscribe-Post: List-Unsubscribe=One-Click
Receivers enforce one-click POST handling and list policy — always validate against a real inbox.
RFC 8058 one-click unsubscribe
Bulk senders should include a List-Unsubscribe header with a mailto address and/or an https URL. RFC 8058 adds List-Unsubscribe-Post: List-Unsubscribe=One-Click so Gmail and other receivers can offer a working unsubscribe button without opening a mail client.
Why QA teams test these headers
- Verify that mailto and https entries render exactly as intended.
- Confirm one-click POST endpoints respond correctly before launch.
- Check that marketing and transactional sends stay compliant.
- Catch typos in generated headers before they reach real subscribers.
Test the full unsubscribe flow
Headers only start the flow. Use temporary inboxes to subscribe with test addresses, receive the campaign, and walk through the unsubscribe and preference-center journey end to end.
Unsubscribe flow testing guideRelated guides
FAQ
List-Unsubscribe header questions
What does the List-Unsubscribe header do?
It tells receiving mail servers a mailto address and/or an https URL a subscriber can use to leave a mailing list, so mail clients can show their own unsubscribe option.
When should I add List-Unsubscribe-Post: List-Unsubscribe=One-Click?
Add it when your https endpoint can process an empty POST, as described in RFC 8058. It lets Gmail-style clients unsubscribe with a single click.
Do I need both a mailto address and an https URL?
No. At least one is required, but sending both is recommended because some clients only support one of the two.
Does this tool send anything to a server?
No. The header block is generated entirely in your browser — nothing is uploaded or stored.
How do I test the resulting headers?
Send a test campaign to a temporary inbox, inspect the raw headers, and click through the unsubscribe or preference-center flow.