List-Unsubscribe header generator and checker (one-click)
One-click unsubscribe needs two headers: List-Unsubscribe with an HTTPS URL (and optionally a mailto: address) in angle brackets, and List-Unsubscribe-Post: List-Unsubscribe=One-Click. Both must be covered by your DKIM signature. Enter your unsubscribe URL to generate them, or paste a message's headers to check what you already send.
Use your platform's per-recipient token in place of {token}. It must accept a POST and unsubscribe without a login or a redirect.
Runs in your browser. Nothing is sent anywhere.
Sample result
These 2 headers give mail from acme.example one-click unsubscribe (RFC 8058).
- One-click unsubscribe
- 2 headers
- HTTPS URI
- 1, with a recipient token
- mailto
- unsubscribe@acme.example
What this means for you
Big mailbox providers expect one-click unsubscribe from bulk senders; add both, signed by DKIM.
- Builds both one-click unsubscribe headers
- Checks pasted headers for one HTTPS URI
- Flags a wrong or missing Post value
- Checks both headers are covered by DKIM
- List-Unsubscribe
- RFC 8058
- Headers
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
How do I add one-click unsubscribe headers?
- To generate: enter the HTTPS URL that unsubscribes a recipient with a single POST, using your platform's per-recipient token. Add an unsubscribe mailbox if you have one.
- Copy the two header lines into your sending setup, or confirm your email platform already adds them.
- To check: switch to Check my headers and paste the full headers of a message you sent (in Gmail: open the message, ⋮, Show original).
- Fix anything marked Fail. The DKIM check needs the full headers, because it reads the h= tag of the DKIM-Signature.
Example
- You enter
- The one-click unsubscribe URL
https://mail.acme.example/unsubscribe/…and the mailboxunsubscribe@acme.example. - You get
- 2 headers for RFC 8058 one-click unsubscribe:
List-Unsubscribewith the HTTPS and mailto URIs, andList-Unsubscribe-Post: List-Unsubscribe=One-Click. - Limits
- No limits; the headers are built or checked in your browser.
What is the List-Unsubscribe header?
It's an email header that tells mail apps how to unsubscribe the reader, so they can show their own Unsubscribe button. List-Unsubscribe, defined in RFC 2369, lists ways to unsubscribe: a mailto: address, a web URL or both, each in angle brackets and separated by commas. Mail apps use it to show their own Unsubscribe button next to the sender's name.
On its own, an HTTPS link only opened a web page, which often asked people to log in or confirm. RFC 8058 added List-Unsubscribe-Post: List-Unsubscribe=One-Click, which tells the mailbox provider it may unsubscribe the person by sending a POST request to that URL, with no page to visit. That's what makes the button one click.
What are the one-click unsubscribe requirements?
One HTTPS URL that identifies the recipient, the exact List-Unsubscribe-Post value, and a DKIM signature covering both headers. RFC 8058 section 3.1 says the header MUST contain one HTTPS URI, the Post header MUST contain exactly List-Unsubscribe=One-Click, and the URI MUST carry enough information to identify the recipient and list, preferably an opaque, hard-to-forge token rather than a plain email address. The sender MUST NOT answer the POST with a redirect, and the request arrives without cookies or login.
Section 4 requires a valid DKIM signature covering both headers, so nobody can add an unsubscribe link to your mail in transit. In practice that means list-unsubscribe and list-unsubscribe-post both appear in the signature's h= tag. You can confirm the signature itself with the DKIM checker.
Is one-click unsubscribe mandatory?
For bulk senders to Gmail and Yahoo, yes, in marketing and subscribed messages. Google's email sender guidelines require senders of more than 5,000 messages a day to Gmail accounts to support one-click unsubscribe in marketing and subscribed messages, and to process unsubscribes within two days. Yahoo's sender requirements say the same for bulk senders. Transactional mail such as receipts and password resets is exempt.
One-click unsubscribe is one part of those requirements, alongside SPF, DKIM, DMARC and a low spam complaint rate. Run the Google and Yahoo bulk sender checker for the DNS side, and read how to add one-click unsubscribe for platform-specific steps.
What is the difference between mailto and one-click unsubscribe?
| mailto: only | HTTPS + List-Unsubscribe-Post | |
|---|---|---|
| What happens on click | The reader's app sends an email | The provider sends a POST to your server |
| Meets Gmail and Yahoo's bulk sender rule | No | Yes, when DKIM covers both headers |
| Works without your server | Yes | No, you need an endpoint |
Who uses this tool, and for what?
- Developers sending through an API or SMTP
- Generate the two header lines, add them to every marketing message, and include both in the DKIM h= list.
- Email marketers
- Paste the headers of a real campaign (Show original in Gmail) to confirm your platform's one-click setup before a big send.
- Deliverability consultants
- Audit a client's message headers in seconds and hand back the exact failing rule from RFC 8058.
- Cold emailers
- Check that your sequencer's unsubscribe link is a real one-click endpoint, not just a footer link, before volume grows.
What can’t this tool tell you?
- It checks the headers, not your endpoint. It can't confirm that a POST to your URL actually unsubscribes anyone.
- The DKIM check reads the h= tag only; it doesn't verify the signature cryptographically. Use the DKIM checker for the key.
- Whether a token is opaque enough is a heuristic: a long mix of letters and digits passes, a plain email address doesn't.
- Mail apps decide for themselves when to show the Unsubscribe button, even when the headers are correct.
Common questions
- What is the List-Unsubscribe header?
- A header defined in RFC 2369 that lists ways to unsubscribe, a mailto: address, an HTTPS URL or both, each in angle brackets. Gmail, Yahoo and Apple Mail use it to show an Unsubscribe link next to the sender, so readers don't have to hunt for one in the footer.
- What does a List-Unsubscribe header example look like?
- Two lines: List-Unsubscribe: <https://example.com/unsubscribe/TOKEN>, <mailto:unsubscribe@example.com?subject=unsubscribe> and List-Unsubscribe-Post: List-Unsubscribe=One-Click. The token should identify the recipient without exposing their email address. The generator above builds both lines for your own URL.
- How do I add a List-Unsubscribe header to Gmail?
- You add it to the messages you send, not to Gmail. Most email platforms add it when one-click unsubscribe is switched on; if you send through your own server or an API, add both headers to each message and include them in the DKIM signature. Then check a sent message here.
- Is one-click unsubscribe mandatory?
- For bulk senders, yes. Google requires it for anyone sending more than 5,000 messages a day to Gmail accounts, in marketing and subscribed messages, and Yahoo has the same requirement. Transactional mail such as receipts and password resets is exempt.
- How does one-click unsubscribe work?
- When the reader presses the mail app's Unsubscribe button, the mailbox provider sends an HTTPS POST with the body List-Unsubscribe=One-Click to the URL in your header. Your server reads the token in the URL, unsubscribes that recipient and returns a success status, without a redirect or a login.
Sources
Authentication and capacity are half of deliverability.
The other half is who you send to. Every hard bounce counts against the domain and inboxes you are sending from, and nothing in DNS can tell you which addresses on your list are dead.
- Bulk verification with real SMTP mailbox checks
- Hard bounces removed before a send, not discovered after
- Catch-all, disposable and role detection on every row
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